U.S. patent application number 12/468467 was filed with the patent office on 2009-09-10 for magnetoresistance effect element, magnetic head, magnetic reproducing apparatus, and magnetic memory.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Hiromi Fuke, Hideaki FUKUZAWA, Hitoshi Iwasaki, Masashi Sahashi, Hiromi Yuasa.
Application Number | 20090225477 12/468467 |
Document ID | / |
Family ID | 30446287 |
Filed Date | 2009-09-10 |
United States Patent
Application |
20090225477 |
Kind Code |
A1 |
FUKUZAWA; Hideaki ; et
al. |
September 10, 2009 |
MAGNETORESISTANCE EFFECT ELEMENT, MAGNETIC HEAD, MAGNETIC
REPRODUCING APPARATUS, AND MAGNETIC MEMORY
Abstract
A magnetoresistance effect element comprises a magnetoresistance
effect film and a pair of electrode. The magnetoresistance effect
film having a first magnetic layer whose direction of magnetization
is substantially pinned in one direction; a second magnetic layer
whose direction of magnetization changes in response to an external
magnetic field; a nonmagnetic intermediate layer located between
the first and second magnetic layers; and a film provided in the
first magnetic layer, in the second magnetic layer, at a interface
between the first magnetic layer and the nonmagnetic intermediate
layer, and/or at a interface between the second magnetic layer and
the nonmagnetic intermediate layer, the film having a thickness not
larger than 3 nanometers, and the film has as least one selected
from the group consisting of oxide, nitride, oxinitride, phosphide,
and fluoride. The pair of electrodes are electrically connected to
the magnetoresistance effect film to supply a sense current
perpendicularly to a film plane of said magnetoresistance effect
film.
Inventors: |
FUKUZAWA; Hideaki;
(Kanagawa-ken, JP) ; Yuasa; Hiromi; (Kanagawa-ken,
JP) ; Fuke; Hiromi; (Kanagawa-ken, JP) ;
Iwasaki; Hitoshi; (Kanagawa-ken, JP) ; Sahashi;
Masashi; (Kanagawa-ken, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Kabushiki Kaisha Toshiba
Tokyo
JP
|
Family ID: |
30446287 |
Appl. No.: |
12/468467 |
Filed: |
May 19, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11931089 |
Oct 31, 2007 |
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12468467 |
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10400690 |
Mar 28, 2003 |
7301733 |
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11931089 |
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Current U.S.
Class: |
360/314 ;
428/811.2; G9B/5.104 |
Current CPC
Class: |
G01R 33/093 20130101;
H01L 27/224 20130101; H01L 43/08 20130101; G11B 5/3906 20130101;
G11C 11/16 20130101; G11B 5/3983 20130101; B82Y 25/00 20130101;
H01F 41/325 20130101; H01F 10/3254 20130101; H01L 27/228 20130101;
G11C 11/161 20130101; H01F 41/303 20130101; H01F 10/3259 20130101;
Y10T 428/1121 20150115; H01F 10/1936 20130101; B82Y 40/00 20130101;
G11B 5/398 20130101; H01F 10/3268 20130101; H01F 10/3281
20130101 |
Class at
Publication: |
360/314 ;
428/811.2; G9B/5.104 |
International
Class: |
G11B 5/33 20060101
G11B005/33; G11B 5/39 20060101 G11B005/39 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2002 |
JP |
P2002-092998 |
Sep 9, 2002 |
JP |
P2002-263251 |
Claims
1. A magnetoresistance effect element comprising: a
magnetoresistance effect film having: a first magnetic layer whose
direction of magnetization is substantially pinned in one
direction; a second magnetic layer whose direction of magnetization
changes in response to an external magnetic field; a nonmagnetic
intermediate layer located between the first and second magnetic
layers; and a film provided in the first magnetic layer, in the
second magnetic layer, at an interface between the first magnetic
layer and the nonmagnetic intermediate layer, or at an interface
between the second magnetic layer and the nonmagnetic intermediate
layer, the film having a thickness not larger than 3 nanometers,
and the film having at least one selected from the group consisting
of oxide, nitride, oxynitride, phosphide, and fluoride; and a pair
of electrodes electrically coupled to the magnetoresistance effect
film and configured to supply a sense current perpendicularly to a
film plane of said magnetoresistance effect film.
2. The magnetoresistance effect element according to claim 1,
wherein a spin filtering takes place when conduction electrons
which constitute the sense current pass near the film so that one
of up spin electrons and down spin electrons preferentially
passes.
3. The magnetoresistance effect according to claim 1, wherein a
Fermi speed of up spin electrons and a Fermi speed of down spin
electrons which constitute the sense current are different in a
region of the first or second magnetic layer, the region adjoining
the film.
4. The magnetoresistance effect element according to claim 1,
wherein a mean thickness of the film is in a range between one
atomic layer and three atomic layers.
5. The magnetoresistance effect element according to claim 1,
wherein the film is formed substantially uniform.
6. The magnetoresistance effect element according to claim 1,
comprising two of the films and the films being formed either two
of the positions in the second magnetic layer, at an interface
between the first magnetic layer and the nonmagnetic intermediate
layer, and at an interface between the second magnetic layer and
the nonmagnetic intermediate layer.
7. The magnetoresistance effect element according to claim 1,
wherein at least one of the first and second magnetic layers is
made of a material having a crystal structure of a face centered
cubic, its film plane is oriented in a direction substantially
parallel to (111) plane, and its orientation dispersion angle is
equal to or smaller than 5 degrees.
8. The magnetoresistance effect element according to claim 1,
wherein at least one of the first and second magnetic layers is
made of a material having a crystal structure of a face centered
cubic, its film plane is oriented in a direction substantially
parallel to (110) plane, and its orientation dispersion angle is
equal to or smaller than 5 degrees.
9. The magnetoresistance effect element according to claim 1,
wherein a product AR of an area A and resistance R is equal to or
smaller than 500 m.OMEGA..mu.m.sup.2, where the area A is an area
of a portion of the magnetoresistance effect film that the sense
current substantially passes through, and the resistance R is a
resistance obtained between the pair of electrodes.
10. The magnetoresistance effect element according to claim 1,
wherein a distance between the neighboring films is in a range
between 0.2 nanometers and 3 nanometers.
11. The magnetoresistance effect element according to claim 2,
wherein at least one of the first and second magnetic layers is
made of a material having a crystal structure of a face centered
cubic, its film plane is oriented in a direction substantially
parallel to (111) plane, and its orientation dispersion angle is
equal to or smaller than 5 degrees.
12. The magnetoresistance effect element according to claim 2,
wherein at least one of the first and second magnetic layers is
made of a material having a crystal structure of a face centered
cubic, its film plane is oriented in a direction substantially
parallel to (110) plane, and its orientation dispersion angle is
equal to or smaller than 5 degrees.
13. The magnetoresistance effect element according to claim 1,
wherein the first or second magnetic layer which includes or
adjoins the film is made of a ferromagnetic material including at
least one selected from the group consisting of iron (Fe), cobalt
(Co), and nickel (Ni).
14. The magnetoresistance effect element according to claim 1,
wherein the film includes at least one element selected from the
group consisting of magnesium (Mg), aluminum (Al), silicon (Si),
calcium (calcium), scandium (Sc), titanium (Ti), vanadium (V),
chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel
(nickel), copper (Cu), zinc (Zn), strontium (Sr), yttrium (Y),
zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru),
rhodium (Rh), palladium (Pd), silver (Ag), barium (Ba), lantern
(La), hafnium (Hf), tantalum (Ta), and tungsten (W).
15. The magnetoresistance effect element according to claim 1,
further comprising a nonmagnetic metal layer adjoining the film and
provided in the first and/or second magnetic layer, the nonmagnetic
metal layer having a thickness equal to or smaller than 2
nanometers.
16. The magnetoresistance effect element according to claim 1,
further comprising a nonmagnetic metal layer adjoining the film and
provided at an interface between the first magnetic layer and the
nonmagnetic intermediate layer, and/or at an interface between the
second magnetic layer and the nonmagnetic intermediate layer, the
nonmagnetic metal layer having a thickness equal to or smaller than
2 nanometers.
17. The magnetoresistance effect element according to claim 1,
further comprising: a magnetic metal layer adjoining the film and
provided in the first and/or second magnetic layer; and a
nonmagnetic layer adjoining the magnetic metal layer, and having a
thickness equal to or smaller than 2 nanometers.
18. The magnetoresistance effect element according to claim 1,
further comprising: a magnetic metal layer adjoining the film and
provided at an interface between the first magnetic layer and the
nonmagnetic intermediate layer, and/or at an interface between the
second magnetic layer and the nonmagnetic intermediate layer; and a
nonmagnetic layer adjoining the magnetic metal layer, and having a
thickness equal to or smaller than 2 nanometers.
19. The magnetoresistance effect element according to claim 17,
wherein the first or second magnetic layer is magnetically coupled
through the film, the magnetic metal layer and the nonmagnetic
metal layer included within its layer.
20. The magnetoresistance effect element according to claim 1,
wherein a distance between the film and the nonmagnetic
intermediate layer is equal to or smaller than three
nanometers.
21. A magnetoresistance effect element comprising: a
magnetoresistance effect film having: a first magnetic layer whose
direction of magnetization is substantially pinned in one
direction; a second magnetic layer whose direction of magnetization
changes in response to an external magnetic field; a nonmagnetic
intermediate layer located between the first and second magnetic
layers; and a film provided in the first magnetic layer, in the
second magnetic layer, at an interface between the first magnetic
layer and the nonmagnetic intermediate layer, or at an interface
between the second magnetic layer and the nonmagnetic intermediate
layer, the film having a thickness not larger than 3 nanometers,
and the film having at least one selected from the group consisting
of oxide, nitride, oxynitride, phosphide, and fluoride; a pair of
electrodes electrically coupled to the magnetoresistance effect
film and configured to supply a sense current perpendicularly to a
film plane of said magnetoresistance effect film.
22. A magnetic reproducing apparatus which reads information
magnetically recorded in a magnetic recording medium, the magnetic
reproducing apparatus comprising a magnetic head having a
magnetoresistance effect element including: a magnetoresistance
effect film having: a first magnetic layer whose direction of
magnetization is substantially pinned in one direction; a second
magnetic layer whose direction of magnetization changes in response
to an external magnetic field; a nonmagnetic intermediate layer
located between the first and second magnetic layers; and a film
provided in the first magnetic layer, in the second magnetic layer,
at an interface between the first magnetic; layer and the
nonmagnetic intermediate layer, or at an interface between the
second magnetic layer and the nonmagnetic intermediate layer, the
film having a thickness not larger than 3 nanometers, and the film
having at least one selected from the group consisting of oxide,
nitride, oxynitride, phosphide, and fluoride; and a pair of
electrodes electrically coupled to the magnetoresistance effect
film and configured to supply a sense current perpendicularly to a
film plane of said magnetoresistance effect film.
23. A magnetic memory comprising a plurality of magnetoresistance
effect elements arranged in a matrix fashion, the magnetoresistance
effect element including; a magnetoresistance effect film having: a
first magnetic layer whose direction of magnetization is
substantially pinned in one direction; a second magnetic layer
whose direction of magnetization changes in response to an external
magnetic field; a nonmagnetic intermediate layer located between
the first and second magnetic layers; and a film provided in the
first magnetic layer, in the second magnetic layer, at an interface
between the first magnetic layer and the nonmagnetic intermediate
layer, or at an interface between the second magnetic layer and the
nonmagnetic intermediate layer, the film having a thickness not
larger than 3 nanometers, and the film having at least one selected
from the group consisting of oxide, nitride, oxinitride, phosphide,
and fluoride; and a pair of electrodes electrically coupled to the
magnetoresistance effect film and configure to supply a sense
current perpendicularly to a film plane of said magnetoresistance
effect film.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2002-092998, filed on Mar. 28, 2002, and the prior Japanese Patent
Application No. 2002-263251, filed on Sep. 9, 2002; the entire
contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a magnetoresistance effect
element, a magnetic head, a magnetic reproducing apparatus, and a
magnetic memory and more particularly, to a magnetoresistance
effect element which has a structure where a sense current is
passed perpendicularly to a film plane of the magnetoresistance
effect film, and to a magnetic head using the same, a magnetic
reproducing apparatus and a magnetic memory.
[0003] By discovery of the Giant MagnetoResistance effect (GMR) in
the laminated structure of magnetic layers, the performance of a
magnetic device, especially a magnetic head is improving rapidly.
Especially application to a magnetic head and MRAM (Magnetic Random
Access Memory) of spin valve film structure (Spin-Valve: SV film)
brought big technical progress to the magnetic device field.
[0004] A "spin valve film" has a structure which sandwiches a
non-magnetic layer between two ferromagnetic layers. The
magnetization of one ferromagnetic layer (called a "pinned layer"
or a "magnetization pinned layer", etc.) is fixed by an
antiferromagnetic layer etc., and the magnetization direction of
another ferromagnetic layer (called a "free layer", a
"magnetization free layer", etc.) is rotatable in a response to an
external magnetic field. And when the relative angle of the
magnetization direction of a pinned layer and a free layer changes,
a giant magnetoresistance change is obtained.
[0005] A CPP (Current-Perpendicular-to-Plane) type
magnetoresistance effect element which passes sense current to a
perpendicular direction to a film plane of such a spin valve film
shows the still larger GMR effect compared with a conventional CIP
(Current-In-Plane) type magnetoresistance effect element which
passes sense current in parallel to a film plane.
[0006] On the other hand, a TMR element using the TMR effect
(Tunneling MagnetoResistance effect) is also developed, which
passes the current to a perpendicular direction as the CPP type GMR
elements. However, in a TMR element, since the tunnel effect is
used, when thickness of the non-magnetic intermediate layer made of
alumina, for example, is made thin, there is a problem that MR rate
of change decreases rapidly.
[0007] In the case of a TMR element, in the state where alumina is
not made thin, resistance is very high. When application to a
magnetic head is considered, its adoption is difficult from a
viewpoint of a shot noise and a high frequency response. For
example, in order to use for a magnetic head, AR (current passed
area.times.element resistance) must be set to 1.OMEGA..mu.m.sup.2
or less. However, in the case of a TMR element, there is a problem
that MR rate of change disappears in this resistance level.
[0008] On the other hand, a CPP type magnetoresistance effect
element has the advantage which has larger MR rate of change
compared with a CIP type magnetoresistance effect element. In the
case of a CPP type element, resistance of an element is dependent
on element area. Therefore, when the miniaturization of the element
is carried out, it also has an advantage that the amount of
resistance change increases. This advantage serves as a big merit
in the present when the miniaturization of a magnetic device
progresses. Therefore, a CPP type magnetoresistance effect element
and the magnetic head using it are considered to be the major
candidates for realizing storage density from 200 gigabits per
square inch (200 Gbpsi) to one Tbits per square inch class.
[0009] In the case of a TMR element, since an insulator is used for
an intermediate layer, element resistance becomes high too much.
For this reason, if the miniaturization of the element area is
carried out, originating in high resistance and causing shot noise
generating peculiar to a tunnel phenomenon and high frequency
response degradation will pose problems. For this reason, a means
of realistic solution is not found in application of a TMR element
in high storage density of 200 or more Gbpsi.
[0010] In MRAM, tolerance level of element resistance is
comparatively wide compared with a magnetic head. It is thought
that a TMR element is applicable to MRAM of a first generation.
However, also in MRAM, the miniaturization of the element area is
carried out with improvement in storage density, and it is expected
that a problem that the resistance becomes too high comes out. That
is, also in any of a magnetic head and MRAM, high resistance
peculiar to a TMR element poses a problem with improvement in
storage density.
[0011] On the other hand, in the case of a CPP element using a
metal non-magnetic intermediate layer, since the element resistance
is very small unlike the TMR elements, the amount of resistance
change is small while MR rate of change is large. As a result, it
is difficult to acquire a high reproduction output signal. And in
the case of spin valve film structure where realization possibility
is the highest, only a free layer and a pinned layer are provided
as the magnetic layers. That is, compared with a case of the
artificial lattice multilayer structure, thickness and interfaces
which contribute to MR rate of change are both insufficient. For
this reason, MR rate of change becomes remarkably small compared
with a practical MR rate of change.
[0012] In order to solve a part of this problem, by laminating an
oxide layer for the CPP element which used the metal non-magnetic
intermediate layer, increase of element resistance is aimed at and
the trial to raise the amount of resistance change as for the same
MR rate of change is made (K. Nagasaka et al., The 8th Joint
MMM-Intermag Conference, DD-10).
[0013] In the case of this method, a metallic low resistance area
is established in pinholes in part of oxide layer, and it aims to
obtain a high resistance by constricting the current. However, it
is difficult to provide pinholes uniformly. Resistance varies
largely especially in a storage density of 100 Gbpsi or more for
which element size of about 0.1 micrometers is needed. For this
reason, fabrication of stable CPP elements is difficult.
[0014] By this technique, an increase in large MR rate of change
cannot be realized, but resistance is just adjusted. That is,
though MR rate of change does not change, if AR is raised, it is
expected that the amount AdR of resistance change expressed with
the product of MR rate of change expressed with percentage and AR
will improve. Since area which contributes to MR rate of change
becomes small effectually, MR rate of change seen from the whole
may increase.
[0015] However, since element size becomes small so that it becomes
high storage density, the resistance demanded from a viewpoint of a
shot noise and the high frequency response characteristic must be
small, for example, a case of storage density of 200 Gbpsi,
tolerance level of AR (current passing area.times.resistance) is
from about one m .OMEGA..mu.m.sup.2 to a few hundreds m
.OMEGA..mu.m.sup.2. On the other hand, in the case of 500 Gbpsi
class storage density, AR must be less than 500
m.OMEGA..mu.m.sup.2. This is because element resistance becomes
large, when the element size accompanying improvement in storage
density contracts. Thus, it is required that AR should be made
small with improvement in storage density. Therefore, it is clear
that there is a limit in an approach to increase AdR (current
passing area.times.resistance change) by increasing AR while
keeping MR at a fixed value. That is, the essential improvement in
the MR rate of change itself is needed with improvement in storage
density.
[0016] In order to improve a situation, research of a half metal
prospers aiming at the essential improvement in MR rate of change.
Generally, it is defined as a "half metal" being a magnetic
material with which only either of the densities of states of a
up-spin electron and a down-spin electron exists near Fermi level.
When an ideal half metal is realized, two states of an infinite
resistance state and a low resistance state are formed
corresponding to the two magnetization states of the pinned layer
and the free layer of an anti-parallel state and a parallel state.
Therefore, MR rate of change of infinite size is ideally
realizable.
[0017] Such an ideal state may be unable to be realized in fact.
However, if a difference of density of states of a up spin electron
and a down spin electron becomes larger than conventional material,
an increase of MR rate of change does not remain in improvement in
about 2 times, but a rise of 3 times, 4 times, and still more
nearly extraordinary fast MR rate of change is expected.
[0018] That is, unlike the conventional solution mentioned above,
improvement in large MR rate of change becomes essentially
possible. However, there is a big problem which obstructs
utilization which is explained below in a half metal investigated
intensively now.
[0019] That is, the following material can be mentioned as a half
metal material investigated until now. CrAs of semiconducting
materials, such as NiMnSb of the CrO2 and the Whistler alloy with
rutile structures, such as FesO.sub.4 with spinel structure,
LaSrMnO with perovskite structure, and LaCaMnO, ZnO, GaNMn. Many of
these materials have a complicated crystal structure. For this
reason, in order to form a high quality crystal, substrate heating
to a high temperature or special film formation technique is
required. There is a problem that these processes are not easy to
carry out in a creation process of an actual magnetoresistance
effect element. This is the first problem.
[0020] A problem mentioned above may be solved by improvement of
film formation technology. However, there are the following
problems as a still more essential problem. That is, any case of
half metal material known until now, a limit of curie temperature
(Tc: in the case of Ferro magnetism) and Neel temperature (Tn: in
the case of ferrimagnetism or antiferromagnetism) is at most 400K
(about 100 degrees in centigrade). Since temperature which shows
half metal nature (here, it is defined as Thm) becomes the lower
temperature side, there is a problem that material which shows half
metal nature in room temperature is not yet found. This is the
second problem.
[0021] Thus, if half metal nature is realizable only at low
temperature, the application to a consumer product is completely
impossible. In order to use it as an actual magnetoresistance
effect element, half metal appearance temperature Thm must be at
least 150-200 degrees in centigrade or higher. In order to make Thm
high, it is required to make Tc or Tn higher. However, with
material investigated until now, Tc or Tn beyond room temperature
hardly exists. Intensive research is made in order to raise Tc and
Tn, but a decisive solution which raises Tc or Tn in every material
cannot be found.
[0022] There are the following problems as the third big problem.
That is, even if a half metal is realized in a single layer film,
when it is provided in a multilayered structure like a spin valve,
there is a problem that half metal nature in a laminated film
interface is lost. This is because band structures differ in a bulk
state in an interface of the lamination structure. Although a half
metal is realized in a single layer film, there is a problem that a
half metal is unrealizable in an interface or the surface. In a
part of magnetic semiconductor material (CrAs), there is a report
that a half metal of high Tc was realized. However, generally in an
interface of a semiconducting material and metal material,
diffusion is intense. For this reason, it is very difficult for
half metal nature to be made not to be lost in a junction
interface.
[0023] When using these magnetic semiconductor material, it is
desirable to also constitute a non-magnetic spacer layer from a
semiconducting material, and the combination with metal material is
not realistic. If a specific material in an interface layer is not
laminated in the case of the Heusler alloy material, such, as
NiMnSb, it is pointed out that half metal nature cannot be
essentially realized (G. A. de Wijs et al., Phys. Rev. B 64,
020402-1). This originates in half metal nature being lost in a
laminated structure interface, since symmetry in band structure of
a crystal collapses near the interface.
[0024] With a CPP element using the Heusler alloy, even if measured
at 4.2K or less cryogenic temperature which is the temperature
below Tc, only MR rate of change lower than a spin valve film
formed with the usual metal is observed. This is based on above
explained problem.
[0025] With spin valve film structure, it must essentially be made
a laminated structure. Since half metal nature will be lost near
the interface, it is meaningless to pursue material which half
metal nature by using a single layer of a single crystal.
[0026] As other means, there is a method of using a half metal as a
material of a spacer layer. Here, a "spacer layer" is a
non-magnetic layer which divides the pinned layer and the free
layer in the case of a CPP element. An improved result using a
perovskite system oxide is reported. For example, although Tc and
Thm are still low temperature, when measured at temperature below
Tc, a TMR element realized quite larger MR rate of change than a
spin valve film of the usual magnetic material (J. Z. Sun et al.,
Appl. Phys. Lett. 69, and 3266 (1996)). However, it is difficult to
create the pinned layer, the spacer layer, and the free layer using
material with a special crystal structure like perovskite. And the
above-mentioned second problem that Tc is low temperature is still
not solved at all.
[0027] Thus, in extension of research of a half metal studied
intensively now, realization of a high MR rate of change is
difficult even in low temperature. Even if it is realized, a still
bigger breakthrough for realizing large MR rate of change at room
temperature will be needed.
SUMMARY OF THE INVENTION
[0028] According to an embodiment of the invention, there is
provided a magnetoresistance effect element comprising: a
magnetoresistance effect film having: a first magnetic layer whose
direction of magnetization is substantially pinned in one
direction; a second magnetic layer whose direction of magnetization
changes in response to an external magnetic field; a nonmagnetic
intermediate layer located between the first and second magnetic
layers; and a film provided in the first magnetic layer, in the
second magnetic layer, at an interface between the first magnetic
layer and the nonmagnetic intermediate layer, or at an interface
between the second magnetic layer and the nonmagnetic intermediate
layer, the film having a thickness not larger than 3 nanometers,
and the film having at least one selected from the group consisting
of oxide, nitride, oxinitride, phosphide, and fluoride; and a pair
of electrodes electrically coupled to the magnetoresistance effect
film and configured to supply a sense current perpendicularly to a
film plane of said magnetoresistance effect film.
[0029] According to other embodiment of the invention, there is
provided a magnetoresistance effect element comprising: a
magnetoresistance effect film having: a first magnetic layer whose
direction of magnetization is substantially pinned in one
direction; a second magnetic layer whose direction of magnetization
changes in response to an external magnetic field; a nonmagnetic
intermediate layer located between the first and second magnetic
layers; and a film provided in the first magnetic layer, in the
second magnetic layer, at an interface between the first magnetic
layer and the nonmagnetic intermediate layer, and/or at an
interface between the second magnetic layer and the nonmagnetic
intermediate layer, and the film having at least one selected from
the group consisting of oxide, nitride, oxinitride, phosphide, and
fluoride; and a pair of electrodes electrically coupled to the
magnetoresistance effect film to supply a sense current
perpendicularly to a film plane of said magnetoresistance effect
film, wherein a product AR of an area A and resistance R is equal
to or smaller than 500 m.OMEGA..mu.m.sup.2, where the area A is an
area of a portion of the magnetoresistance effect film that the
sense current substantially passes through, and the resistance R is
a resistance obtained between the pair of electrodes, or a
resistance R between the pair of electrodes is equal to or smaller
than 100.OMEGA..
[0030] According to other embodiment of the invention, there is
provided a magnetic head comprising a magnetoresistance effect
element having; a magnetoresistance effect film having: a first
magnetic layer whose direction of magnetization is substantially
pinned in one direction; a second magnetic layer whose direction of
magnetization changes in response to an external magnetic field; a
nonmagnetic intermediate layer located between the first and second
magnetic layers; and a film provided in the first magnetic layer,
in the second magnetic layer, at an interface between the first
magnetic layer and the nonmagnetic intermediate layer, or at an
interface between the second magnetic layer and the nonmagnetic
intermediate layer, the film having a thickness not larger than 3
nanometers, and the film having at least one selected from the
group consisting of oxide, nitride, oxinitride, phosphide, and
fluoride; and a pair of electrodes electrically coupled to the
magnetoresistance effect film and configured to supply a sense
current perpendicularly to a film plane of said magnetoresistance
effect film.
[0031] According to other embodiment of the invention, there is
provided a magnetic head comprising a magnetoresistance effect
element having; a magnetoresistance effect film having: a first
magnetic layer whose direction of magnetization is substantially
pinned in one direction; a second magnetic layer whose direction of
magnetization changes in response to an external magnetic field; a
nonmagnetic intermediate layer located between the first and second
magnetic layers; and a film provided in the first magnetic layer,
in the second magnetic layer, at an interface between the first
magnetic layer and the nonmagnetic intermediate layer, and/or at an
interface between the second magnetic layer and the nonmagnetic
intermediate layer, and the film having at least one selected from
the group consisting of oxide, nitride, oxinitride, phosphide, and
fluoride; and a pair of electrodes electrically coupled to the
magnetoresistance effect film to supply a sense current
perpendicularly to a film plane of said magnetoresistance effect
film, wherein a product AR of an area A and resistance R is equal
to or smaller than 500 m.OMEGA..mu.m.sup.2, where the area A is an
area of a portion of the magnetoresistance effect film that the
sense current substantially passes through, and the resistance R is
a resistance obtained between the pair of electrodes, or a
resistance R between the pair of electrodes is equal to or smaller
than 100.OMEGA..
[0032] According to other embodiment of the invention, there is
provided a magnetic reproducing apparatus which reads information
magnetically recorded in a magnetic recording medium, the magnetic
reproducing apparatus comprising a magnetic head having a
magnetoresistance effect element including: a magnetoresistance
effect film having: a first magnetic layer whose direction of
magnetization is substantially pinned in one direction; a second
magnetic layer whose direction of magnetization changes in response
to an external magnetic field; a nonmagnetic intermediate layer
located between the first and second magnetic layers; and a film
provided in the first magnetic layer, in the second magnetic layer,
at an interface between the first magnetic layer and the
nonmagnetic intermediate layer, or at an interface between the
second magnetic layer and the nonmagnetic intermediate layer, the
film having a thickness not larger than 3 nanometers, and the film
having at least one selected from the group consisting of oxide,
nitride, oxinitride, phosphide, and fluoride; and a pair of
electrodes electrically coupled to the magnetoresistance effect
film and configured to supply a sense current perpendicularly to a
film plane of said magnetoresistance effect film.
[0033] According to other embodiment of the invention, there is
provided a magnetic reproducing apparatus which reads information
magnetically recorded in a magnetic recording medium, the magnetic
reproducing apparatus comprising a magnetic head having a
magnetoresistance effect element including: a magnetoresistance
effect film having: a first magnetic layer whose direction of
magnetization is substantially pinned in one direction; a second
magnetic layer whose direction of magnetization changes in response
to an external magnetic field; a nonmagnetic intermediate layer
located between the first and second magnetic layers; and a film
provided in the first magnetic layer, in the second magnetic layer,
at an interface between the first magnetic layer and the
nonmagnetic intermediate layer, and/or at an interface between the
second magnetic layer and the nonmagnetic intermediate layer, and
the film having at least one selected from the group consisting of
oxide, nitride, oxinitride, phosphide, and fluoride; and a pair of
electrodes electrically coupled to the magnetoresistance effect
film to supply a sense current perpendicularly to a film plane of
said magnetoresistance effect film, wherein a product AR of an area
A and resistance R is equal to or smaller than 500
m.OMEGA..mu.m.sup.2, where the area A is an area of a portion of
the magnetoresistance effect film that the sense current
substantially passes through, and the resistance R is a resistance
obtained between the pair of electrodes, or a resistance R between
the pair of electrodes is equal to or smaller than 100.OMEGA..
[0034] According to other embodiment of the invention, there is
provided a magnetic memory comprising a plurality of
magnetoresistance effect elements arranged in a matrix fashion, the
magnetoresistance effect element including: a magnetoresistance
effect film having: a first magnetic layer whose direction of
magnetization is substantially pinned in one direction; a second
magnetic layer whose direction of magnetization changes in response
to an external magnetic field; a nonmagnetic intermediate layer
located between the first and second magnetic layers; and a film
provided in the first magnetic layer, in the second magnetic layer,
at an interface between the first magnetic layer and the
nonmagnetic intermediate layer, or at an interlace between the
second magnetic layer and the nonmagnetic intermediate layer, the
film having a thickness not larger than 3 nanometers, and the film
having at least one selected from the group consisting of oxide,
nitride, oxinitride, phosphide, and fluoride; and a pair of
electrodes electrically coupled to the magnetoresistance effect
film and configure to supply a sense current perpendicularly to a
film plane of said magnetoresistance effect film.
[0035] According to other embodiment of the invention, there is
provided a magnetic memory comprising a plurality of
magnetoresistance effect elements arranged in a matrix fashion, the
magnetoresistance effect element including: a magnetoresistance
effect film having: a first magnetic layer whose direction of
magnetization is substantially pinned in one direction; a second
magnetic layer whose direction of magnetization changes in response
to an external magnetic field; a nonmagnetic intermediate layer
located between the first and second magnetic layers; and a film
provided in the first magnetic layer, in the second magnetic layer,
at an interface between the first magnetic layer and the
nonmagnetic intermediate layer, and/or at an interface between the
second magnetic layer and the nonmagnetic intermediate layer, and
the film having at least one selected from the group consisting of
oxide, nitride, oxinitride, phosphide, and fluoride; and a pair of
electrodes electrically coupled to the magnetoresistance effect
film to supply a sense current perpendicularly to a film plane of
said magnetoresistance effect film, wherein a product AR of an area
A and resistance R is equal to or smaller than 500
m.OMEGA..mu.m.sup.2, where the area A is an area of a portion of
the magnetoresistance effect film that the sense current
substantially passes through, and the resistance R is a resistance
obtained between the pair of electrodes, or a resistance R between
the pair of electrodes is equal to or smaller than 100.OMEGA..
[0036] According to embodiment of the invention, a magnetic field
detection with a high sensitivity can be stably obtained and a
magnetic head having a high output and high S/N even at a high
recording density and a magnetic reproducing apparatus, and a
magnetic memory of the degree of high integration can be realized
with low power consumption, and the merit on industry is great.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The present invention will be understood more fully from the
detailed description given herebelow and from the accompanying
drawings of the embodiments of the invention. However, the drawings
are not intended to imply limitation of the invention to a specific
embodiment, but are for explanation and understanding only.
[0038] In the drawings:
[0039] FIG. 1 is a schematic diagram for explaining the basic
concept of the invention;
[0040] FIG. 2A is a schematic diagram showing band structure of the
usual half metal, and FIG. 2B is a schematic diagram showing band
structure acquired by very thin oxide layer in the invention;
[0041] FIGS. 3A through 3C are conceptual diagrams for explaining a
difference between a physical principle of CCP, and a physical
principle of spin filtering by a very thin oxide layer TB of the
invention;
[0042] FIG. 4 is a principal part sectional view showing structure
where a non-magnetic layer NM is provided in the upper and lower
sides of the very thin oxide layer TB;
[0043] FIG. 5 is a principal part sectional view which expresses a
modification of structure expressed to FIG. 4, and expresses
structure where a non-magnetic layer NM of a very thin is inserted
only in one side among the upper and lower sides of a very thin
oxide layer TB;
[0044] FIG. 6 expresses a case where a very thin oxide layer TB is
inserted in an interface of a pinned layer P (or a free layer F)
and a spacer layer S;
[0045] FIG. 7 is a schematic diagram showing a structure where a
very thin oxide layer TB is provided in the opposite side of a
pinned layer P (or a free layer F) from the spacer layer S;
[0046] FIG. 8 expresses structure where a very thin oxide layer TB
was inserted into a pinned layer P (or a free layer F)
[0047] FIG. 9 is a schematic diagram showing structure where a very
thin non-magnetic layer NM and a metal magnetic layer FM are
provided only in one of the upper and lower sides of a very thin
oxide layer TB;
[0048] FIG. 10 illustrates structure where a very thin oxide layer
TB is inserted in an interface of a pinned layer P (or a free layer
F) and a spacer layer S;
[0049] FIG. 11 illustrates structure where a very thin oxide layer
TB is inserted in an interface by the side of opposite as a spacer
layer S of a pinned layer P (or a free layer F);
[0050] FIG. 12 is a schematic diagram showing a case where portions
being unreacted (un-oxidized, un-nitrided, non-fluoridated) are
contained in a very thin oxide layer TB;
[0051] FIG. 13 is a schematic diagram showing a case where
unreacted metallic elements exist uniformly in a very thin oxide
layer TB as the form not of granular but a more detailed cluster
TB;
[0052] FIGS. 14A through 14D are sectional schematic diagrams which
illustrate insertion locations of a very thin oxide layer TBC;
[0053] FIGS. 15A through 15D are schematic diagrams which
illustrate structures where a very thin oxide layer TB is inserted
in both pinned layer P and free layer F;
[0054] FIGS. 16A through 16D are schematic diagrams showing
examples where a very thin oxide layer TB is inserted in an inside
of a pinned layer P or a free layer F;
[0055] FIGS. 17A through 17D show the structures where the very
thin oxide layers TB are inserted in both a pinned layer P and a
free layer F;
[0056] FIGS. 18A through 18D show the structures where the very
thin oxide layers TB are provided in both inside the bulk and near
the interface in a pinned layer P or a free layer F;
[0057] FIGS. 19A through 19D show the structures where two or more
very thin oxide layers TB are inserted in either a pinned layer P
or a free layer F, in order to aim at interface dependence
scattering and the bulk scattering effect, and to reinforce the
bulk scattering effect;
[0058] FIGS. 20A through 20D egress element structures which aimed
at the interface scattering effect in either a pinned layer P or a
free layer F, and aimed at the bulk scattering effect by two or
more very thin oxide layers TB in a layer of another side;
[0059] FIGS. 21A through 21D illustrate further structures where
two or more very thin oxide layers TB are inserted in order to aim
at both the interface scattering effect and the bulk scattering
effect also in either a pinned layer P or a free layer F, and to
heighten the bulk scattering effect further in one of layers;
[0060] FIGS. 22A through 22C are schematic diagrams which
illustrate laminated constitutions of magnetoresistance effect
elements which can be used in the invention;
[0061] FIGS. 23A and 23B are schematic diagrams which illustrate
spin valve structures where a pinning layer is provided;
[0062] FIG. 24 is a conceptual diagram showing an example of a
formation apparatus which forms a magnetoresistance effect element
containing a very thin oxide layer TB in the embodiment;
[0063] FIG. 25 is a sectional view of the magnetoresistance effect
element cut in parallel to the medium facing surface P which is
opposite to a magnetic recording medium (not shown);
[0064] FIG. 26 is a sectional view of the magnetic resistance
effect element cut in the perpendicular direction to the medium
opposite side P;
[0065] FIG. 27 is a perspective view that shows outline
configuration of this kind of magnetic reproducing apparatus;
[0066] FIG. 28 is a perspective view of a magnetic head assembly at
the distal end from an actuator aim 155 involved, which is viewed
from the disk;
[0067] FIG. 29 is a conceptual diagram which exemplifies the matrix
structure of the magnetic memory of the embodiment;
[0068] FIG. 30 is a conceptual diagram showing another example of
the matrix structure of the magnetic memory of the embodiment;
[0069] FIG. 31 is a conceptual diagram showing a principal part of
the cross sectional structure of a magnetic memory according to an
embodiment of the invention; and
[0070] FIG. 32 shows the A-A' line sectional view.
DETAILED DESCRIPTION
[0071] Unlike a TMR element, a CPP element is excellent in a shot
noise or a high frequency response. In a CPP element, in order to
obtain sufficient output without causing element resistance
increase, essential increase in MR rate of change is needed. For
that purpose, it is required to use a half metal with a high rate
of spin polarization for a pinned layer or a free layer, or for
both a pinned layer and a free layer.
However, realization of a half metal with Tc (or Tn) beyond room
temperature needed for actual application is difficult with the
conventional half metal technology. That is, realization of a high
MR rate of change near the room temperature is difficult.
[0072] Then, in the invention, a new material structure which shows
half metal nature in a room temperature with the spin valve
structure has been examined. If such completely new material
structure is realized, a high MR rate of change can be realized.
Therefore, a high AdR can be realized, without increasing the
resistance. Then a magnetoresistance effect element showing a large
resistance change dR and a large output voltage is realized. As the
result, a magnetoresistance effect element suitable for a
high-density recording, a magnetic head using it, magnetic
reproducing apparatus (Hard Disk Drive etc.) that carries it, and
MRAM having a large capacity can be offered.
[0073] All the half metal material studied now was material with
low Tc. Conversely, there was a problem that the rate of spin
polarization was low in the case of the material which has a high
Tc. Although the rate of spin polarization is low, the following
materials can be mentioned as a material with high Tc:
That is, iron (Fe), cobalt (Co) and nickel (Ni) which have
ferromagnetism, and alloy materials which contain any these
elements as a main component can be mentioned. These materials have
a Tc of hundreds of degrees in centigrade, and have a very stable
magnetism even at high temperatures.
[0074] A inventors have considered whether the half metal
characteristic is realizable by using alloy materials which contain
these elements as a main component. Such materials base on a simple
bcc (body centered cubic) metal, fee (face centered cubic) metal,
or hcp (hexagonal close-packed) metal.
[0075] The inventors have greatly convened the way of thinking from
the conventional approach toward a half metal. And in order to
enlarge the rate of spin polarization of electronic conduction in
materials having high Tc, the invention has been made.
[0076] That is, as mentioned above, in the conventional approach
for a half metal, it does not start from a laminated structure like
a spin valve but premised on the material which has half metal
nature in a single layer. As a result, the creation of material
which has a complicated crystal structure and low Tc has been
studied, and the approach of creating spin valve structure like CPP
or TMR was taken using those materials. That is, creating an
artificial material was not performed. According to such a
conventional approach, many problems arise as explained above.
[0077] The inventors noted that hair metal nature was a phenomenon
resulting from band structure of a crystal. Then, the inventors
resulted in a conclusion that half metal nature can be realized
also in a high temperature beyond room temperature even in a spin
valve structure which used the conventional high Tc metal material
as a base by performing delicate band modulations. Specifically, a
very thin layer of an oxide, a nitride, an oxinitride, a phosphide,
or a fluoride layer of a thickness of about 0.2 nm -3 nm is
inserted into a ferromagnetic layer having a high Tc. Thus, it was
found out that MR rate of change of the CPP characteristic
increased greatly, without causing a rise in resistance. It is
thought that MR rate of change improved according to the band
modulation effect.
[0078] In research of the conventional half metal material in a
complicated crystal structure, half metal nature is greatly lost
near the interface which changes crystal band structure. On the
other hand, the invention bases on the approach to use the
conventional magnetic material of high Tc, and to realize a half
metal nature by using an interfacial phenomenon induced by the very
thin oxide layer (or a nitride, an oxinitride, a phosphide, or a
fluoride layer). In this case, since the material of high Tc is
used from the beginning unlike the approach of the conventional
half metal research, efforts to raise Tc are unnecessary.
[0079] In the specification, the very thin layers aiming at band
modulation such as oxide, nitride, fluoride, etc. are called "a
very thin oxide layer TB." However, also when it is called a very
thin oxide layer TB, it may not be limited to an oxide layer but
may include a nitride layer, an oxinitride layer, a phosphide
layer, and a fluoride layer. It becomes possible to produce the
artificial band modulation effect by a very thin oxide layer TB.
Then, two or more layers are inserted into a ferromagnetic layer,
or a surprising band structural change is attained by changing a
lamination cycle etc. at variety. It becomes possible as the result
to create many artificial substances. Compared with the approach
which forms a complicated crystal structure which has been made
conventionally, many artificial substances can be far formed with a
realistic means using the thin film formation technology which can
be mass-produced.
[0080] First, material of a pinned layer and a free layer is
explained. For this material, 3d transition metals which have
sufficiently high (hundreds of degrees in centigrade) Tc can be
used as a base. Specifically, magnetic metal material with Tc
beyond room temperature, such as iron (Fe), cobalt (Co), nickel
(nickel), these alloys, and these alloys including still another
element can be used as a base.
[0081] If such material is used as a base, a problem of Tc will
completely be lost. Usually, although there are few differences in
density of states of up spin electron and down spin electron in
such materials, and the difference is very small it cannot be
called "half metal nature." This has determined a limit of MR rate
of change of the conventional CPP spin valve stricture. That is,
although a problem of Tc temperature was removed, a rate of spin
polarization needs to be increased.
[0082] However, when inserting a very thin oxide layer into such
common magnetic metal material, band structure of a magnetic metal
near the oxide layer shows a big change. That is, it is expected
easily that band structure changes greatly when oxygen or a
nitrogen element combines with metallic elements. However, if the
usual metal oxide material is formed thickly, resistance in case an
electron passes the layer at the time of perpendicular current
passing will become high. With the oxide in these comparatively
thick films, it is expected simply that half metal nature cannot be
realized.
[0083] Since it will become like a tunnel barrier if thickness of
an oxide layer aiming at band modulation becomes thick, the
increase of resistance is produced. However, band structure of a
magnetic metal material near the very thin oxide layer can be
modulated, without causing large increase of resistance, when
thickness of the oxide layer is thin enough. Since high Tc
magnetism metal material is used as a base when such a very thin
oxide layer is used, half metal nature can be advantageously
realized even at room temperature.
[0084] FIG. 1 is a schematic diagram for explaining the basic
concept of the invention. As expressed in this figure, spin valve
structure is based on laminated structure where a spacer layer S is
inserted between a pinned layer P and a free layer F. These pinned
layer P and a free layer F consist of a ferromagnetic substance
which used iron (Fe), cobalt (Co), nickel (nickel), or manganese
(Mn) with high Tc or Tn as a base. In the invention, a very thin
oxide layer TB is inserted into a pinned layer P and/or a free
layer F which consists of these ferromagnetic substances.
[0085] Then, band structure changes near this very thin oxide layer
TB, and a rate of a spin polarization of a conduction electron
which passes that interface improves rather than the conventional
ferromagnetic substance material of high Tc or high Tn.
Consequently, the half-metal-like characteristic is realized and MR
rate of change of a CPP element improves. As band structure
acquired here, it does not need to be limited by narrow definition
like the conventional half metal. The reason is explained
below.
[0086] FIG. 2A is a schematic diagram showing band structure of the
usual half metal, and FIG. 2B is a schematic diagram showing band
structure acquired by very thin oxide layer in the invention.
Namely, in this figure (a) and (b), the vertical axis expresses the
energy, the left-hand side of the horizontal axis expresses the
density of states of the down spin electrons, and the right-hand
side of the horizontal axis express the density of states of the up
spin electrons, respectively.
[0087] According to the definition of the conventional "half
metal", the conditions where density of states (DOS) exist in
either an up spin electron or a down spin electron correspond to a
"half metal." However, when pursuing half metal nature as the
conduction characteristic, such conditions are not necessarily
required.
[0088] A model of DOS by definition of the conventional "half
metal" is shown in FIG. 2A. In the case of an example expressed in
this figure, only density of states of an up spin electron exists,
and density of states of a down spin electron does not exist near
the Fermi level.
Since only electrons near the Fermi level can contribute to
conduction, only an up spin electrons can contribute to conduction
and down spin electrons cannot contribute it in this situation. For
this reason, it is called a "half metal."
[0089] Only from a viewpoint of such DOS, search of the half metal
material by band calculation etc. has so far been performed. If
this viewpoint is persisted in, a half metal which uses iron (Fe),
cobalt (Co), or nickel (nickel) as a base will not be proposed.
[0090] However, what is required for a CPP element is that a half
metal nature is obtained when electrons are made to conduct. And in
order to fill this demand, severe conditions that one of DOS of a
up spin electron or a down spin electron does not exist completely
at the Fermi level are not needed.
[0091] That is, as expressed in FIG. 2B, a spin polarization does
not have to be carried out completely. As shown in Table 1, in a
CPP element, a difference of the Fermi speed of an up spin electron
and a down spin electron is required. If a difference of the Fermi
speed of an up spin electron and a down spin electron is large, a
ratio of a conduction electron contributed to conduction will
spread more greatly than a difference of an up spin electron
expected only from a viewpoint of simple DOS, and a down spin
electron.
[0092] Since a difference of the Fermi speed of an up spin electron
and a down spin electron will be effective as a difference of the
second power if it is converted into conduction, it appears as a
very big effect (I. I. Main, Phys. Rev. Lett., 83 (7), 1999, p
1427). When this effect is taken into consideration, it turns out
that a difference of DOS of an up spin electron and a down spin
electron near the Fermi level does not necessarily need to be close
to 100%. In other wards, a definition of a half metal from a
viewpoint of the conventional DOS is a sufficient condition, but if
it thinks from a viewpoint of electronic conduction, it is not a
necessary condition. By taking a difference of the electronic Fermi
speed into consideration, it becomes a necessary condition.
[0093] However, material search of the half metal characteristic on
band calculation taken into consideration to the Fermi speed was
not made at all. Even if taken into consideration to a difference
of the Fermi speed of an up spin and a down spin, in material which
shows the conventional high Tc, a half metal nature as conduction
was not realized. MR rate of change in alloy material which used as
a base simple iron (Fe), cobalt (Co), and nickel (nickel)
investigated so far was remarkably lower than MR rate of change
which should be realized by half metal. That is, in a spin valve
element using material which used the conventional high Tc
ferromagnetism material as a base, a certain means to change the
Fermi speed was not considered at all.
[0094] On the other hand, the inventors noted that the Fermi speed
also originated in band structure of a crystal deeply. And it was
discovered that conduction half metal nature was realized by
producing band modulation in a magnetic material layer which used
to high Tc material as a base. Here, if an oxide or a nitride,
oxinitride, phosphide, and fluoride are used, band modulation can
be effectively produced by using very small quantity of them. Then,
in order to acquire the band modulation effect, a very thin oxide
layer TB by such material was invented.
[0095] In order not to raise resistance of an element, it must be
made for these very thin oxide layer TB to have to bring about the
band modulation effect in the sufficiently thin state. Progress of
film formation technology in recent years can realize now creation
of an artificial lattice of an oxide layer of such a very thin, or
a nitride layer. When thought only on the conventional film
formation technical level, such an artificial lattice was what
cannot be realized at all.
This is also the cause as which an artificial substance which
inserted a very thin oxide layer of such was not devised. An
inventors was able to establish technology which forms an oxide
layer of a very thin into a magnetic material, and was able to
result in a the invention based on a result that these artificial
substances' being formed and a rate of spin polarization change a
lot.
[0096] As an effect of a very thin oxide layer TB in the invention,
as explained above, as expressed in FIG. 2B, 100% polarization of
DOS must not necessarily be realized and an effect which a
difference produces at the Fermi speed should just be acquired. The
Fermi speed of an up spin electron and a down spin electron is
determined by situation of a Fermi surface. Therefore, if band
structure changes with very thin oxide layers TB, these Fermi speed
will also change.
[0097] As explained above, in the invention, the band modulation
effect is acquired by inserting a very thin oxide layer TB. This
very thin oxide layer TB can be formed with an oxide, a nitride, an
oxinitride, the phosphide, or fluoride.
[0098] Here, the very thin oxide layer TB in the invention differs
from a filter layer for resistance adjustment which is provided for
mere "current constriction (CCP (Current Confined Path)) in
respects of a function and a physical principle.
[0099] Such a filter layer for resistance adjustment has pinholes
of a certain rate. That is, it is the oxide layer (or a nitride
layer, a fluoride layer) which is not uniform. On the other hand, a
very thin oxide layer TB of the invention has low resistance
itself, or hardly causes a resistance rise for sufficiently thin
thickness. It does not have a role to adjust resistance with the
ratio or area of pinholes, etc. In the invention, it is not so
preferred from a viewpoint of band modulation that deviation of a
current path comes out. As for a very thin oxide layer TB in the
invention, it is preferred that it is the uniform oxide layer (or a
nitride layer, a fluoride layer) which does not have pinholes.
[0100] Here, a "uniform" oxide layer shall mean that a pinhole
average diameter is less than 20% to the sum of thickness of a free
layer, a non-magnetic spacer layer, and a pinned layer. As the
measuring method, the TEM (transmission electron microscope)
observation can be used, for example. As the manufacture method to
form a uniform very thin oxide layer TB, the ion beam oxidizing
method, a plasma oxidation method, the radical oxidizing method, a
high energy oxidization method using a gas cluster ion beam, etc.
can be used as will be mentioned later.
[0101] As for mean thickness of a very thin oxide layer TB, it is
preferred that it is the range of 0.2 nm -3 nm. Here, "mean
thickness" is the average value when observing five points at
intervals of 5 nm toward the direction of a film plane. A sectional
TEM photograph of an element etc. can be used for this measurement.
A definition about this "mean thickness" shall be the same for each
layer, such as non-magnetic layer NM, as will explained in full
detail behind.
[0102] As the very thin oxide layer TB, if a layer made of oxide,
nitride, oxinitride, phosphide or fluoride of thickness of an about
0.2 nm is provided, sufficient effect will be obtained depending on
selection of a proper material. By insertion of a uniform very thin
oxide layer TB, since current flows uniformly, the spin filtering
effect can also be expected.
[0103] FIGS. 3A through 3C are conceptual diagrams for explaining a
difference between a physical principle of CCP, and a physical
principle of spin filtering by a very thin oxide layer TB of the
invention.
[0104] FIG. 3A shows a case where a very thin oxide layer TB is
inserted in a pinned layer P in the embodiment. FIG. 3B shows the
structure where an oxide layer for CCP is inserted in a pinned
layer P, and FIG. 3C shows the structure where an oxide layer for
CCP is inserted in a spacer layer S.
[0105] As shown in FIGS. 3B and 3C, since the oxide layer for CCP
is provided for a current constriction and for a filter for
resistance adjustment, the thin current path CP is provided in the
oxide layer. When electrons pass the current path CP intermittently
provided into the oxide layer, both an up spin electron US and a
down spin DS pass the current path CP. That is, a spin dependence
effect is not produced, in this case, a rise of MR rate of change
is acquired according to an effect of the current constriction.
For this current constriction purpose, the oxide layers for CCP are
divided into portions which passes current, and portions which
block current, as shown in the figures.
[0106] On the other hand, in the case of a very thin oxide layer TB
by the embodiment, the electronic spin filtering effect arises
according to the band modulation effect. That is, the
spin-depending conduction characteristic for which a down spin
electrons DS are hard to pass although the up spin electrons US
easily pass, is obtained.
[0107] A large MR rate of change can be obtained according to an
effect of spin filtering, without raising resistance.
[0108] Hereafter, the embodiment of the invention will be
explained, referring to the drawings.
[0109] In a the invention, as expressed in FIG. 1, by inserting a
very thin oxide layer TB, a state of a pinned layer P and/or a free
layer F can be changed, and high MR rate of change and a high
output signal can be realized. The very thin oxide layer TB can be
inserted in the pinned layer and/or in the free layer and/or at the
interfaces between these layers and the spacer layer.
[0110] In the invention, a non-magnetic layer of a very thin may be
inserted between the very thin oxide layer TB and the ferromagnetic
layer.
[0111] FIG. 4 is a principal part sectional view showing structure
where a non-magnetic layer NM is provided in the upper and lower
sides of the very thin oxide layer TB. That is, this figure
expresses structure where a very thin oxide layer TB is inserted
into the pinned layer P or the free layer F, and a very thin
non-magnetic layer NM is further inserted for both the upper and
lower sides thereof.
[0112] Since thickness of this non-magnetic layer NM is thin
enough, upper and lower parts of the ferromagnetic layer P (F) are
magnetically coupled by sufficient strength via the very thin oxide
layer TB and the non-magnetic layer NM. A form of this magnetic
coupling may be a ferromagnetic coupling or a antiferromagnetic
coupling. And in order to obtain sufficient magnetic coupling of
upper and lower parts of the ferromagnetic layer P (F), the very
thin oxide layer TB and the non-magnetic layer NM need to be both
sufficiently thin. When the band modulation effect is aimed at,
sufficient effect can be acquired even if the non-magnetic layer is
made very thin. Mean thickness of a very thin oxide layer TB is
preferably from about 0.2 nm to 3 nm. In order to prevent a
degradation of the magnetic coupling between magnetic layers of the
upper and lower sides, as for thickness of the non-magnetic layer
NM, it is still more desirable that it is from about 0.2 nm to 1
nm.
[0113] As for sum total thickness of a very thin oxide layer TB and
a non-magnetic layer NM, it is desirable from 0.4 nm to 3 nm, and
more desirably from 0.4 nm to 2 nm. The reason is that magnetic
coupling of the magnetic layers of the upper and lower sides
through the non-magnetic layer and the very thin oxide layer will
become weak if thickness of the non-magnetic NM becomes thick. That
is, a non-magnetic layer NM in the embodiment is not aiming at an
effect as a barrier layer for making oxygen of a very thin oxide
layer not touch a magnetic layer from a viewpoint of soft magnetism
etc.
[0114] Material which is later mentioned about Table 5 as a
material of a very thin oxide layer TB is desirable. As a material
of the non-magnetic layer NM, aluminum (Al), copper (Cu), gold
(Au), silver (Ag), ruthenium (Ru), rhodium (Rh), iridium (Ir),
rhenium (Re), titanium (Ti), vanadium (V), chromium (Cr), manganese
(Mn), magnesium (Mg), tantalum (Ta), tungsten (W), or hafnium (Hi)
is desirable, and it is especially desirable to use copper (Cu),
gold (Au), or silver (Ag).
[0115] Insertion of a non-magnetic metal layer NM of these very
thins provides a metal layer other than a ferromagnetic layer in a
thin oxide layer TB interface. Therefore, the way of contribution
of the band modulation effect changes and the spin filtering effect
becomes strong.
[0116] A loss of a spin memory of electrons which flow in a very
thin oxide layer TB from ferromagnetic layer P (F) etc. can be
controlled by inserting a non-magnetic metal layer NM.
[0117] In any case, it becomes possible by providing a non-magnetic
layer NM to enlarge further the increase effect of MR rate of
change by a very thin oxide layer TB.
[0118] FIG. 5 is a principal part sectional view which expresses a
modification of structure expressed to FIG. 4, and expresses
structure where a non-magnetic layer NM of a very thin is inserted
only in one side among the upper and lower sides of a very thin
oxide layer TB. Also in this example of transformation, it may be
the same as that of what was mentioned above about FIG. 4 about
material, thickness, etc. of a very thin oxide layer TB and a very
thin non-magnetic layer NM.
[0119] FIG. 6 expresses a case where a very thin oxide layer TB is
inserted in an interface of a pinned layer P (or a free layer F)
and a spacer layer S. Also in this case, a non-magnetic layer NM of
a very thin can be provided between a very thin oxide layer TB and
a pinned layer P (a free layer F). About the function, it is the
same as that of what was mentioned above about FIGS. 4 and 5.
[0120] FIG. 7 is a schematic diagram showing a structure where a
very thin oxide layer TB is provided in the opposite side of a
pinned layer P (or a free layer F) from the spacer layer S. It is
the same as that of what mentioned above about FIGS. 4 and 5 about
that function also in this structure. In this case, since a
magnetic layer does not necessarily exist via a non-magnetic layer
NM and a very thin oxide layer TB, the magnetic coupling between
the upper and lower sides do not need to be cared about. However,
from a viewpoint of the band modulation effect, the desirable
thickness range of a non-magnetic layer NM and a very thin oxide
layer TB is the same as that of what has so far been shown.
[0121] In order to acquire an effect of the invention fully, the
structure where a very thin oxide layer exists in a magnetic layer
film, or the structure where a very thin oxide layer exists in an
interface with a spacer layer as shown in FIGS. 4 through 6 is more
preferable than the structure of FIG. 7 where a very thin oxide
layer exists in a position most distant from the spacer layer S.
Structures shown in FIGS. 5 through 10 mentioned later are also
more preferred than a structure shown in FIG. 11 by same reason.
For example, as for a very thin oxide layer, it is desirable to be
located within 3 nm from a non-magnetic spacer layer.
[0122] Moreover, the same effect is acquired by inserting the very
thin oxide layer in a pin layer or a free layer. It is more
effective to insert in a pin layer at this time than to insert in a
free layer. That is because the magnetization response of the free
layer may fall on device operation, when the very thin oxide layer
is inserted in the interface or the inside of the free layer. In
particular, this poses an essential problem, when providing the
very thin non-magnetic layer NM in addition to the very thin oxide
layer TB, And it becomes difficult to use it in .eta. and a free
layer.
[0123] FIGS. 8 through 11 are principal part sectional views which
illustrate structures where a metal magnetic layer FM is further
provided between a very thin non-magnetic layer NM and a very thin
oxide layer TB.
[0124] First, FIG. 8 expresses structure where a very thin oxide
layer TB was inserted into a pinned layer P (or a free layer F).
And a metal magnetic layer FM is laminated at the upper and lower
sides of a very thin oxide layer TB, and a ferromagnetic layer is
further laminated at the outside via a very thin non-magnetic
layer. By providing such a magnetic layer FM, as mentioned above
about FIG. 4, material which adjoins a very thin oxide layer TB is
made to be changed suitably, and the band modulation effect of a
very thin oxide layer TB can be emphasized.
[0125] In the case of this example, by inserting a metal magnetic
layer FM, a magnetic effect in inside of a very thin oxide layer TB
is assisted, and an effect which promotes magnetic coupling of a
pinned layer P of the upper and lower sides through a very thin
oxide layer TB (a free layer F) is acquired.
[0126] On the other hand, when a very thin oxide layer TB is formed
by self-oxidization (or a self-nitride, self-fluoridation, etc.) of
a metal layer, this metal magnetic layer FM may correspond to a
portion which remained as that non-oxidized portion. In such a
case, a laminated structure of a very thin oxide layer TB and a
metal magnetic layer FM can be formed, keeping good the adjustment
of an interface of a very thin oxide layer TB and a metal layer
FM.
[0127] Next, FIG. 9 is a schematic diagram showing structure where
a very thin non-magnetic layer NM and a metal magnetic layer FM are
provided only in one of the upper and lower sides of a very thin
oxide layer TB. That is, a very thin oxide layer TB is inserted
into a pinned layer P (or a free layer F), and a metal magnetic
layer FM and a non-magnetic layer NM are laminated at the bottom.
Also in this case, an effect mentioned above about FIGS. 4 through
FIG. 8 is acquired.
[0128] FIG. 10 illustrates structure where a very thin oxide layer
TB is inserted in an interface of a pinned layer P (or a free layer
F) and a spacer layer S. That is, the same effect as what was
mentioned above about FIGS. 4 through 9 is acquired by inserting a
metal magnetic layer FM and a non-magnetic layer NM also in this
case.
[0129] FIG. 11 illustrates structure where a very thin oxide layer
TB is inserted in an interface by the side of opposite as a spacer
layer S of a pinned layer P (or a free layer F). The same effect as
what was mentioned above about FIGS. 4 through 9 is acquired by
inserting a metal magnetism layer FM and a non-magnetic layer NM
also in this case. In this case, since a magnetic layer does not
necessarily exist via a non-magnetic layer NM and a very thin oxide
layer TB, magnetic coupling between the upper and lower sides do
not need to be cared about. However, from a viewpoint of the band
modulation effect, the desirable thickness ranges of a non-magnetic
layer NM and a very thin oxide layer TB are the same as that of
what has so far been shown.
[0130] On the other hand, although it is preferred that it is a
uniform oxide film as for a very thin oxide layer TB used in the
embodiment. However, it is not limited to this, and the oxide layer
TB may not oxidized completely. This is the same in the case of
most fundamental structure that does not contain a very thin
non-magnetic layer NM as illustrated in FIG. 1.
[0131] FIG. 12 is a schematic diagram showing a case where portions
being unreacted (un-oxidized, un-nitrided, non-fluoridated) are
contained in a very thin oxide layer TB. That is, in the case of an
example of this figure, a very thin oxide layer TB has a reacted
portion TBR in where metal have reacted (oxidization, a nitride,
fluoridation, etc.), and a portions TBM where metal etc. remains in
the unreacted state. The unreacted portions TBM may exist in the
form of a cluster, or in the form of granular, as illustrated in
FIG. 12.
[0132] Thus, if the unreacted metal portions TBM are made to remain
in a film, resistance of a conduction to pass electrons through the
very thin oxide layer TB perpendicularly can be reduced.
When a very thin oxide layer TB consists of oxides (or a nitride,
fluoride, etc.) of a magnetic element, those which remain in a film
as unreacted metallic elements (TBM) is a magnetic element. In this
case, it is effective in maintaining magnetism in a very thin oxide
layer TB, and an effect of helping magnetic coupling of a magnetic
layers of the upper and lower sides through a very thin oxide layer
TB is acquired.
[0133] When metallic elements remain, current tends to flow the
unreacted portions TBM preferentially. In this case, if the
remaining metal element is a magnetic metal which is surrounded by
the reacted portion TBR, increase of the spin filtering effect may
arise, and MR rate of change may increase further.
[0134] As magnetic metallic elements which are easy to remain in
the unreacted state in the very thin oxide layer TB, iron (Fe),
cobalt (Co), nickel (nickel), etc. can be mentioned. Especially
among these, since cobalt (Co) cannot oxidize most easily, in
forming a very thin oxide layer TB by oxidation reaction, cobalt
(Co) tends to remain in an unreacted metal state. As an element
which constitutes a part for such an unreacted metal portions TBM,
non-magnetic metallic elements, such as copper (Cu), gold (Au),
silver (Ag), a ruthenium (Ru), rhodium (Rh), and rhenium (Re), can
also be mentioned.
[0135] FIG. 13 is a schematic diagram showing a case where
unreacted metallic elements exist uniformly in a very thin oxide
layer TB as the form not of granular but a more detailed cluster
TBC. Thus, also when unreacted metallic elements are uniformly
distributed in a very thin oxide layer TB by the shape of a
detailed cluster, an effect homogeneous as what was mentioned above
about FIG. 12 can also be expected. About a kind of metallic
elements which are easy to form a cluster TBC of an unreacted
state, it is the same as that of what was mentioned above about
FIG. 12.
[0136] FIGS. 14A through 14D are sectional schematic diagrams which
illustrate insertion locations of a very thin oxide layer TB. That
is, FIGS. 4A and 4C express examples where a very thin oxide layer
TB is inserted near the interface with a spacer layer S of a free
layer F or a pinned layer P, respectively. In this case,
spin-dependent interface scattering will contribute to improvement
in MR rate of change greatly. By providing a very thin oxide layer
TB, band structure of a magnetic layer F (or P) which is in contact
with a spacer layer S changes. And when an electron which
contributes to conduction carries out spin polarization greatly to
either a up or a down state, MR rate of change improves.
[0137] When based on interface scattering, effect for a
ferromagnetic layer F (or P) which is in contact with a spacer
layer S with the sufficient band modulation effect by a very thin
oxide layer TB must be given. For this reason, as for thickness T
of a ferromagnetic layer between a very thin oxide layer TB and a
spacer layer S, it is preferred not to become not much thick. When
thickness T is 1 nm or less, the "interface effect" is acquired
near the interface with a spacer layer S which is expressed in
FIGS. 14A through 14D. On the other hand, when it is inserted in an
inside of a magnetic layer, the "bulk scattering effect" is
acquired as will be explained later with reference to FIG. 16.
[0138] As the thinnest limit, the structures where the very thin
oxide layer TB is inserted in an interface of a pinned layer P or a
free layer F, and a spacer layer S, are shown in FIGS. 14B and 14D,
as cases of thickness T of 0 nm. An effect which modulates the band
structure of not only the pinned layer P and/or the free layer F
but also the spacer layer S can be obtained in these cases, and the
modulation effect may become more remarkable depending on material
of the spacer layer S.
[0139] FIGS. 15A through 15D are schematic diagrams which
illustrate structures where a very thin oxide layer TB is inserted
in both pinned layer P and free layer F. Since the interface effect
by band modulation arises in two locations in the element in the
case of these examples, the rise effect of MR rate of change will
improve further.
[0140] A very thin oxide layer TB may be inserted not only at the
interface of a pinned layer P or a free layer F, and a spacer layer
S but also inside of the pinned layer P or the free layer F. Thus,
a half metal nature inside the pinned layer P and/or the free layer
F may be emphasized.
[0141] FIGS. 16A through 16D are schematic diagrams showing
examples where a very thin oxide layer TB is inserted in an inside
of a pinned layer P or a free layer F.
[0142] That is, FIGS. 16A and 16B express examples where a very
thin oxide layer TB is inserted in an inside of a pinned layer P or
a free layer F.
In this case, it is possible to produce the spin dependence bulk
scattering effect inside a pinned layer P or a free layer F. In
order to pull out this effect still more notably, a two or more
very thin oxide layer TB can be inserted into the magnetic
layer.
[0143] FIGS. 16C and 16D express examples where two or more very
thin oxide layers TB are inserted in this way. In this case, it is
desirable to insert in the ferromagnetic layers by making an
interval of very thin oxide layers TB into about 0.2 nm to 3 nm.
Since band structure will change with the interval and the period
of the very thin oxide layers TB, half metal nature, i.e., MR rate
of change, will change. Any number of laminations of the very thin
oxide layers TB in a pinned layer P and a free layer F may be
adopted. Actually, about two layers to fifteen layers are
desirable.
[0144] As illustrated in FIGS. 17A through 17D, when the very thin
oxide layers TB are inserted in both a pinned layer P and a free
layer F, an effect of half metal nature improves further.
[0145] As illustrated in FIGS. 18A through 18D, the very thin oxide
layers TB may be provided in both inside the bulk and near the
interface in a pinned layer P or a free layer F.
[0146] In this case, the spin-dependent interface scattering effect
(FIGS. 14 and 15J in a spacer layer interface , and the
spin-dependent bulk scattering effect (FIGS. 16 and 17) inside a
pinned layer P or free layer F, are both acquired, and even higher
MR rate of change can be expected.
[0147] Supposing half metal nature in an interface is in a perfect
ideal state, scattering of either an up spin electron or a down
spin electron will be carried out 100% (all) by the interface.
Therefore, combination with the bulk scattering effect should not
have a meaning. However, it is difficult to realize a completely
ideal state with an actual element in many cases. Therefore, the
further improvement in MR rate of change can be desired by the
addition of half metal nature within the bulk.
[0148] FIGS. 18A through 18D express element structures of a pinned
layer P or a free layer F which is for acquiring interface
dependence scattering and the bulk scattering effect only in one
side either.
[0149] On the other hand, FIGS. 19A through 19D show the structures
where two or more very thin oxide layers TB are inserted in either
a pinned layer P or a free layer F, in order to aim at interface
dependence scattering and the bulk scattering effect, and to
reinforce the bulk scattering effect.
[0150] FIGS. 20A through 2D express element structures which aimed
at the interface scattering effect in either a pinned layer P or a
free layer F, and aimed at the bulk scattering effect by two or
more very thin oxide layers TB in a layer of another side.
[0151] FIGS. 21A through 21D illustrate further structures where
two or more very thin oxide layers TB are inserted in order to aim
at both the interface scattering effect and the bulk scattering
effect also in either a pinned layer P or a free layer F, and to
heighten the bulk scattering effect further in one of layers.
[0152] The invention is not limited to combination illustrated in
FIGS. 14A through 21D. Based on these views, various combinations
where a very thin oxide layer TB is inserted in a pinned layer P
and a free layer F can be considered freely.
[0153] When providing two or more layers of very thin oxide layers
TB, material of these very thin oxide layers may be the same kind,
or materials of these layers TB may be mutually different.
[0154] Easiest spin valve structures were illustrated in FIGS. 14A
through 21D. However, with the application of the invention, the
same function effect can be acquired in various kinds of other
element structures.
[0155] FIGS. 22A through 22C are schematic diagrams which
illustrate laminated constitutions of magnetoresistance effect
elements which can be used in the invention.
[0156] That is, an example expressed in FIG. 22A is the spin valve
structure of the so-called "bottom type" where a pinned layer P is
provided in the bottom (side near a substrate which is not
illustrated).
[0157] FIG. 22B is the spin valve structure of the so-called "top
type" where a pinned layer P is provided in the top (side far from
a substrate which is not illustrated).
[0158] FIG. 22C expresses a spin valve structure of the so-called
"dual spin valve type" where pinned layers P are provided in the
upper and lower sides of a free layer F via a spacer layer S,
respectively.
[0159] The invention can be applied to any these element
structures, and can acquire the same effect. The invention is
applicable also to an element of structure like an "artificial
lattice type" where three or more layers for example, of spacer
layers established besides these. That is, also in these element
structures, a function of a very thin oxide layer TB is the same as
that of what was illustrated to FIGS. 14A through 21D.
[0160] By the way, in spin valve structure, the direction of
magnetization of a free layer F changes to an external magnetic
field. In contrast to this, about a pinned layer P, it is
preferable to provide a pinning layer for adhering the
magnetization direction of the pinned layer so that the
magnetization direction may not change to an external magnetic
field .
[0161] FIGS. 23A and 23B are schematic diagrams which illustrate
spin valve structures where a pinning layer is provided. That is,
as expressed in FIG. 23A, the magnetization direction of a pinned
layer P can be directly adhered with an antiferromagnetic film AF
or a hard magnetic film HM. Alternatively, as expressed in FIG.
23B, so-called "synthetic structure" may be adopted.
[0162] In synthesizer tick structure, the magnetization of the
ferromagnetic layer FM is fixed by the antiferromagnetic film AF,
and via the antiferromagnetic coupling film AC which consists of
ruthenium (Ru) etc., it is coupled to the pinned layer P in
antiferromagnetic fashion, so that the magnetization of the pinned
layer p is fixed.
[0163] In the invention, any pinning means illustrated in FIGS. 23A
and 23B can be used. On the other hand, as a concrete material of a
very thin oxide layer TB, an oxide or a nitride which is easy to
cause band change greatly can be mentioned. In this case, an oxide
layer or a nitride layer containing 3d transition metal which is
easy to cause band change is especially preferred as the material
of the very thin layer.
[0164] Specifically, the oxide, nitride, oxinitride, phosphide, or
fluoride of an element, such as calcium (calcium), scandium (Sc),
titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron
(Fe), cobalt (Co), nickel (nickel), copper (Cu), strontium (Sr),
yttrium (Y), barium (Ba), lantern (La), hafnium (Hf), and tungsten
(W) can be mentioned. Also except these, an oxide or nitrides of an
element such as zinc (Zn), zirconium (Zr), niobium (Nb), molybdenum
(Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), tantalum (Ta),
iridium (Ir), and platinum (Pt) can also be used.
[0165] Except iron oxide (Fe.sub.3O.sub.4), all oxides and nitrides
of these elements were thought not to show a half metal nature so
far.
[0166] In the case of iron oxide (Fe.sub.3O.sub.4), in order to
realize the bulk-characteristic as Fe.sub.3O.sub.4 material,
thickness more than one unit cell was needed in the state of spinal
structure. On the other hand, in the case of an iron oxide, in the
invention, it is not necessary to have spinel structure. In the
invention, a very thin film of 1 through 5 mono layers (atomic
layers) may be sufficient to obtain the effect. At such a thickness
range, it is difficult to define the spinel structure. Even if the
thickness is larger than 5 mono layers, it may be used as long as
the resistance is kept low. Actually, it may be allowable if the
thickness of less than 10 mono layers. In order to obtain a lower
resistance, it is desirable to make the thickness not exceeding 5
mono layers.
[0167] The term "a mono layer (atomic layer)" means the number of
existing layers of oxygen, nitrogen, phosphorous and fluoride which
exists in the direction of thickness, when the film is observed
from the film section. It is defined as average mono thickness by
average value of mono layer thickness measured about five points at
intervals of 5 nm. A sectional TEM of an element can be used as a
concrete observation means. If these compounds are crystalline, the
atomic layers can be counted on the lattice image of TEM.
[0168] Conventionally, an oxide, a nitride, and fluoride with
sufficient periodic structure were inserted. On the other hand, in
a the invention, it is possible to obtain the effect by using a
layer of an oxide, a nitride, a phosphide, or a fluoride whose mean
thickness is below 2 unit cell, and even in the case of mean
thickness below 1 unit cell, for example.
[0169] In the invention, the very thin oxide layer TB itself is not
necessarily made to produce half metal nature, as mentioned above.
In the invention, a ferromagnetic layer (a pinned layer P or a free
layer F) of high Tc which is in contact with a very thin oxide
layer TB is made to produce half metal nature. Therefore, in the
invention, an effect is acquired by using a very thin layer. When
it aims at resistance adjustment or a current constriction, a
sufficient effect cannot be acquired by using such a very thin
layer.
[0170] Since the invention aims at the band modulation effect in a
ferromagnetic layer (a pinned layer P, a free layer F), without
producing a rise of resistance, the oxide layer (or nitride layer)
need to be formed in a sufficient thin thickness which does not
bring about the resistance rise effect.
[0171] Specifically, the thickness is desirably 0.2 nm to 1 nm.
Even if thick, it is 2 nm or less, and it is required to be 3 nm or
less as the greatest tolerance level according to material.
[0172] Iridium (Ir), platinum (Pt), etc. with a large atomic number
tend to produce a spin orbital interaction among elements used as a
very thin oxide layer TB. Therefore, since a spin memory loss
arises, it is not desirable.
[0173] On the other hand, element resistance AR of a CPP element is
need to be less than 500 m.OMEGA..mu.m.sup.2, and preferably lower
than 300 m.OMEGA..mu.m.sup.2, and is the high integration is aimed
at, it is preferably lower than 200 m.OMEGA..mu.m.sup.2. When
computing AR from an actual element, AR is computed as a
multiplication of an effective area A of a current passing portion
of a spin valve film and a resistance R of a CPP element.
[0174] Here, element resistance R can be determined by a direct
measurement calculation from the magnetoresistance effect element.
On the other hand, an effective area A of a current passing portion
of a spin valve film is the quantity depending on the shape of the
magnetoresistance effect element. For example, when the whole spin
valve film is specified as an area which carries out sensing
effectually, element area of the whole spin valve film can be
specified as an current passing area A of a spin valve film. In
this case, element area of a spin valve film should have become
equal to or less than 0.09 .mu.m.sup.2 from a viewpoint of moderate
element resistance.
[0175] However, area of an electrode which is in contact with the
upper and lower sides of a spin valve film prescribes the current
passing effective area of a spin valve film, and when the pattering
of the spin valve film is not carried out, area of an electrode of
the top of bottom may be the current passing area. When areas of
the upper and lower electrodes are different, area of an electrode
of the smaller one may define the effective area. In this case,
element area of a spin valve film should have become also equal to
or less than 0.09 .mu.m.sup.2 from a viewpoint of moderate element
resistance.
[0176] It may not be easy to determine a strict current passing
area depending on the element structure or form of the electrodes.
In this specification, a contact area of an electrode of the one
where a contact area is smaller is adopted as the current passing
effective area A among upper and lower electrodes.
[0177] In the invention, 100 ohms or less are realizable as a value
of raw resistance R between electrodes of a magnetoresistance
effect element. If this is not a magnetoresistance effect element
by the invention, it is not easily to realize this resistance.
Resistance here is the value of resistance between 2 terminals of
an electrode pad reproduction element part of a head which is
equipped at the tip of HGA (Head Gimbal Assembly) in the case of a
head.
[0178] Hereafter, the embodiment of the invention will be explained
in more detail referring to the examples.
First Example
[0179] The magnetoresistance effect element which has the following
laminated structure was formed as the first example of the
invention.
[0180] A lower electrode/tantalum (Ta) 3 nm/nickel iron chromium
(NiFeCr) 5 nm/platinum manganese (PtMn) 10 nm/cobalt iron (CoFe) 4
nm/ruthenium (Ru) 0.9 nm/cobalt iron (CoFe) [4 nm/very thin oxide
layer 0.5 nm/cobalt iron (CoFe) 1 nm/copper (Cu) 5 nm/cobalt iron
(CoFe) 1 nm/nickel iron cobalt (NiFeCo)/copper (Cu) 1 nm/tantalum
(Ta) 5 nm/upper electrode.
[0181] This example has structure where a very thin oxide layer TB
is provided only near the interface with a spacer layer S of a
pinned layer P, as shown in FIG. 14C.
[0182] In a case of this structure, 100 m.OMEGA..mu.m.sup.2 to 200
m.OMEGA..mu.m.sup.2 is obtained as AR, and 5 m.OMEGA..mu.m.sup.2 to
30 m.OMEGA..mu.m.sup.2 is obtained as AdR. Moreover, if the AR rise
effect by the current constriction is combined, 500
m.OMEGA..mu.m.sup.2 may be obtained as AR and 25
m.OMEGA..mu.m.sup.2 to 150 m.OMEGA..mu.m.sup.2 may be obtained as
AdR, as will be explained later.
[0183] If a very thin oxide layer TB is inserted not only near the
interface with a spacer layer S, but also into the pinned layer P
and thus, the bulk scattering effect is used, about 1.5 rimes to 10
times of the above-mentioned value can be obtained. Further, an
effect of being 1.5 times to 10 times many is acquired by inserting
a very thin oxide layer TB in an interface between a free layer F
and a spacer layer S.
[0184] Here, tantalum (Ta) 3 mm/nickel iron chromium (NiFeCr) 5 nm
are the base layers which served both as the buffer effect and the
seed effect. As a material with a buffer effect like tantalum (Ta),
titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), chromium
(Cr), molybdenum (Mo), tungsten (W), and those alloy material may
be used instead of tantalum (Ta).
[0185] An oxide or a nitride of such metals may be used. In this
case, it is not preferred that resistance goes up as CPP structure.
Therefore, in the case of an oxide, it is desirable to make it a
very thin layer 2 nm or less. In the case of a nitride, it is
desirable to make it a conductive nitride of low resistance, or to
make it a very thin layer 2 nm or less, when its resistance is
high.
[0186] Concentration of chromium (Cr) in nickel iron chromium
(NiFeCr) can be made into about 0-40%. fcc metal, hcp metal, etc.
can also be used instead of nickel iron chromium (NiFeCr).
[0187] For example, copper (Cu), zirconium (Zr), ruthenium (Ru),
rhodium (Rh), palladium (Pd), silver (Ag), nickel (nickel), cobalt
(Co), platinum (Pt), gold (Au), osmium (Os), rhenium (Re), and
those alloy material can be used.
[0188] As thickness of these base layers, 3 nm -10 nm or less is
desirable. Material with seed effects other than such material can
also be used. Since AdR of CPP changes with the crystalline
differences arising from a base layer, material selection of a base
layer is important, as will be explained in more detail later.
[0189] Table 2 shows the examples of a base layer. Here, in the
case of the so-called "top type" with which a pinned layer P is
provided in the top from a free layer F, a base layer which has an
oxide layer for current constriction effect may be used. CPP
resistance can be adjusted by constricting the current which flows
the so-called spin dependence scattering unit (important unit of
three layers which brings about MR change) of a pinned layer P, a
spacer layer S, and a free layer F. Simultaneously, though MR rate
of change is same level, AdR can be increased by increasing A. When
storage density is not so high, it may be used as a means to raise
resistance.
[0190] Platinum manganese (PtMn) currently formed on a base layer
is antiferromagnetic material, and is used to fix the magnetization
direction of a magnetic layer formed on it. Instead of platinum
manganese (PtMn), a gamma-Mn system antiferromagnetic film of a
(manganese Mn) rich system, such as palladium platinum manganese
(PdPtMn), iridium manganese (IrMn), and ruthenium rhodium manganese
(RuRhMn) may be used. As thickness of this antiferromagnetic layer,
5 nm -20 nm is desirable, and it is still more desirable that it is
within a range of 7 nm -15 nm.
[0191] The cobalt iron (CoFe) 4 nm/ruthenium (Ru) 0.9 nm /cobalt
iron (CoFe) 4 nm/very thin oxide layer 0.5 nm/cobalt iron (CoFe) 1
nm/on the antiferromagnetic layer are pinned layer P. Here, the
lower platinum manganese (PtMn) 10 nm/cobalt iron (CoFe) 4 nm
/ruthenium (Ru) 0.9 nm are made to call a pinning layer to fix the
magnetization of the pinned layer P. In the example, "synthetic
structure" where the magnetization directions cancel mutually via a
ruthenium (Ru) is adopted.
[0192] The so-called "single layer pin structure" where cobalt iron
(CoFe) 4 nm/ruthenium (Ru) 0.9 nm is removed is also employable
instead of synthetic structure. However, the synthetic structure is
more desirable. In the case of synthetic structure, the fixed
unidirectional magnetic field is large. Since the magnetization
direction through a ruthenium (Ru) is reverse in the case of
synthetic structure, a net magnetic moment which contributes to a
disclosure magnetic field to the film exterior is small, and thus
it is advantageous on device operation. In the case of synthetic
structure, as a magnetic layer between an antiferromagnetic film
and a ruthenium (Ru), alloy material, such as iron cobalt (FeCo),
nickel iron (NiFe), iron (Fe), cobalt (Co), and nickel (nickel),
can be used besides cobalt iron (CoFe).
[0193] Moreover, the magnetization adherence method of having used
hard ferromagnetism films other than the magnetization adherence
direction using an antiferromagnetic film, such as CoPt and CoPtCr,
can be used. In this case, a hard ferromagnetic film can be used
instead of PtMn. Or a hard ferromagnetic film can be used instead
of synthesizer tick structure. When the magnetization is fixed by
using a hard ferromagnetic film, the merit that resistance of an
element can be lowered is obtained. That is, compared with a metal
film of comparatively high resistance like PtMn, CoPt is low
resistance. It becomes possible to reduce the excessive resistance
between upper and lower electrodes, and MR rate of change can be
raised.
[0194] In the case of synthetic structure, the thickness of a
magnetic layer (here CoFe4) between a ruthenium (Ru) and platinum
manganese (PtMn) is desirably to have little asymmetry with
magnetic thickness (saturation-magnetization.times.thickness: Bsxt
[T nm]) of the pinned layer P formed on a ruthenium (Ru) (if the
magnetic thickness is almost equal). This is because H.sub.uaflat
can be enlarged.
[0195] H.sub.uaflat is the size of a magnetic field at which
magnetization pinning of a pinned layer can maintain its
magnetization, when a magnetic field is impressed to an opposite
direction to the magnetization pinned direction of the pinned
layer. In this case, magnetization of a free layer is easily
suitable in the magnetic field impression direction in a lower
field. Therefore, H.sub.uaflat may be the strength at which a
relation of the magnetization directions of a free layer and a
pinned layer can maintain an anti-parallel state (high resistance
state of a spin valve).
[0196] Here, in a resistance-magnetic field curve, a place where a
decrease in 3% from the greatest high resistance state occurs is
defined as H.sub.uaflat. In order to enlarge contribution of spin
dependence scattering, the thickness of the pinned layer P is
preferably made thicker. However, since magnetization pinning by
the PtMn becomes weak in this case, therefore, there is a limit in
a thickness of the pinned layer P.
[0197] In order to obtain H.sub.uaflat which satisfies the above
two requirements, and having a level at which satisfactory head
operation is ensured, the magnetic thickness of a magnetic layer
between the antiferromagnetic layer and ruthenium (Ru) is
preferably from 4T nm to 12T nm, and more preferably from 6T nm to
10T nm.
[0198] The physical thickness at that time will change by Bs of a
magnetic layer, however, is preferably in a range or 2 nm -6 nm,
and more preferably in a range of 3-5 nm.
[0199] Table 3 shows examples of the pinning layer.
[0200] The cobalt iron (CoFe) 4 nm/very thin oxide layer 0.5
nm/cobalt iron (CoFe) 1 nm/on the ruthenium (Ru) layer is the
pinned layer P, which directly contributes to the MR ratio.
[0201] In the case of the conventional magnetoresistance effect
element, a pinned layer was formed only of a metal layer of a
simple cobalt iron (CoFe) layer, and a nickel iron (NiFe) layer,
nickel iron cobalt (NiFeCo layer) and an iron cobalt (FeCo) layer.
On the other hand, in this example, a very thin oxide layer is
provided between two cobalt iron (CoFe) layers.
[0202] Table 4 shows a typical material of a pinned layer P to
which the very thin oxide layer TB is inserted. That is, it is
possible to use not only cobalt iron (CoFe) but also various kinds
of laminated structures which are listed on Table 4. A formation
method of a very thin oxide layer TB will be explained in full
detail behind, referring to FIG. 24.
[0203] Table 5 shows examples of concrete materials of the very
thin oxide layer TB. The band modulation effect is acquired by
using an oxide, a nitride, a oxinitride, a phosphide, or a fluoride
which contains at least one of the elements which are listed on
Table 5, as the material of a very thin oxide layer TB. If an oxide
with which at least one contains 3d transition metal elements, such
as Ti, Cr, V, Mn, Fe, Co, nickel, and Cu, also in it, and an oxide
which contains at least one element among Al, Si, and Mg is used,
it is easily compatible in an effect of band modulation, and an
effect of low resistance.
[0204] Ta, Zr, Hf, Zn, etc. are also desirable material for the
very thin oxide layer TB. As for the thickness of the layer TB,
since it is not desirable to raise resistance, it is preferably in
a range of 0.2 nm-3 nm, and more preferably in a range of 0.2 nm -2
nm, and still more preferably in a range of 0.5 nm-1 nm. When
thickness of a very thin oxide layer is comparatively as thick as
2-3 nm, in order not to raise resistance, the inside of a very thin
oxide layer does not oxidized, nitrided or oxinitrided completely,
and it may be desirable that they are the phosphide or
fluoride.
[0205] When very thin oxide layers are 2-3 nm, comparatively thick
oxide, nitride, or oxinitride layer, it is desirable to have an
element which remains into a very thin oxide layer with a metal
state combined neither with oxygen nor nitrogen (element in the
state where it has not combined with oxygen or nitrogen). In this
case, it is because a rise of resistance is not caused even if
thickness is thick. In this case, it is desirable that Co remains
in the very thin oxide layer with a metal state. When Co remains,
the magnetic coupling of the upper and lower sides through a very
thin oxide layer inside of a pinned layer or a free layer can be
kept good, even if the thickness of a very thin oxide layer is
comparatively thick.
[0206] It is more desirable for a two or more layers of thin very
thin oxide layers to exist rather than, a very thin oxide layer of
a comparatively thick single layer exists in a magnetic layer.
Especially this is because the bulk scattering effect by spin
filtering in a magnetic layer which carried out spin dependence can
be acquired without raising resistance. When it aims at the bulk
scattering effect in the pinned layer or the free layer, it is
especially preferred to have a 2-6 layers of very thin oxide layers
TB. However, when providing a single very thin oxide layer for
spin-dependent interface scattering, even a single layer may
exhibit a greatest effect.
[0207] As concrete experiment data, the data of the element where a
single layer of the very thin oxide layers was inserted into the
pin layer is shown below.
[0208] When a very thin oxide layer is 0.5 nm in thickness, AR was
about 200 m.OMEGA..mu.m.sup.2. The MR rate of change when the main
element which constitutes a very thin oxide layer is changed are as
follows.
[0209] In the case of Co, it was 5%. In the case of nickel, it was
2.5%. In the case of Fe, it was 15%. In the case of aluminum, it
was 10%. In the case of Ti, it was 11%. In the case of Cr, it was
8%. In the case of V, it was 12%. In the case of Zr, it was 13%. In
the case of Mo, it was 12%. In the case of Hf, it was 14%. In the
case of Ta, it was 14%.
[0210] It is more advantageous to insert in a pin layer rather than
a free layer, when inserting a very thin oxide layer, as mentioned
above. It is for preventing the degradation of the response to the
medium magnetic field of a free layer. It becomes still more
remarkable when the very thin non-magnetic layer NM is used
together.
[0211] In a free layer, when the very thin non-magnetic layer NM is
used together, at least 1 nm or more of thickness of the magnetic
layer of each top and bottom through the very thin oxide layer TM
and the very thin non-magnetic layer NM is required, and more
desirably 2 nm or more is required.
[0212] Moreover, as mentioned above, when inserting a single very
thin oxide layer into a pin layer, the increasing rate of MR may
depend on the positions to insert. For example, in the first
example mentioned above, instead of the pin structure having 4 nm
(CoFe)/0.5 nm of very thin oxide layer/1 nm (CoFe), a structure of
2 nm (CoFe)/0.5 nm of very thin oxide layer/2 nm (CoFe) can be
used. In this alternative structure, MR ratio may decrease, since
the very thin oxide layer becomes more remote from the space
layer.
[0213] When the main element of a very thin oxide was Hf,
specifically, MR rate of change of the structure of the first
example was 14%. On the other hand, in the case of 2 nm (CoFe)/0.5
nm of very thin oxide layer/2 nm (CoFe), MR rate of change falls
down to 10%.
[0214] The same phenomenon was observed in the case where Co was
used as the main element of the very thin oxide layer. That is, as
the very thin oxide layer becomes closer to the space layer, the MR
rate becomes larger. That is, the structures as shown in FIG. 16C
and FIG. 16D are more desirable than structure as shown in FIG.
18A. As for the insertion point of the very thin oxide layer,
specifically, it is desirable to set it as the range of less than 2
nm from a spacer layer. It is more desirable to be within 1 nm from
a spacer layer. It is the same even when a very thin oxide layer is
inserted in a free layer. That is, it is desirable that a very thin
oxide layer exists within 2 nm from a spacer layer, and more
desirable that the layer is within 1 nm place from the spacer
layer.
[0215] When it is insufficient to insert a single very thin oxide
layer near the spacer layer, two or more layers very thin oxide
layers can be inserted to obtain further improvement. By inserting
a very thin oxide layer also in the place separated from the spacer
layer rather than 2 nm, MR rate of change goes up further. When
inserting two or more very thin oxide layers, the material of each
very thin oxide layer can be changed. However, when the main
element used as the mother material of a very thin oxide layer is
not a non-magnetic element but a magnetic element like Fe and
nickel, even if it is inserted in the place separated from the
spacer layer rather than 2 nm, the effect of sufficient MR rise may
be demonstrated.
[0216] In the first example mentioned above, the thickness range
from which the thickness of a very thin oxide layer becomes the
optimal according to RA. For example, when the main element which
constitutes a very thin oxide layer is Hf and thickness is 0.5 nm,
RA is 200 m.OMEGA..mu.m.sup.2, and MR rate of change is 14%. When
the thickness of a very thin oxide layer is 0.2 nm, RA is 150
m.OMEGA..mu.m.sup.2 and MR rate of change is 10%. When the
thickness of a very thin oxide layer is 1 nm, RA is 250
m.OMEGA..mu.m.sup.2, and MR rate of change is 14%. When the
thickness of a very thin oxide layer is 2 nm, RA is 300
m.OMEGA..mu.m.sup.2 and MR rate of change is 14%. When the
thickness of a very thin oxide layer is 3 nm, RA is 500
m.OMEGA..mu.m.sup.2 and MR rates of change was 10%.
[0217] If the very thin oxide layer becomes thicker, RA becomes
larger. On the other hand, if the thickness of a very thin oxide
layer becomes thick, MR becomes also larger. However, if a very
thin oxide layer becomes thick too much, MR rate of change may
fall.
[0218] The existence of such a very thin oxide layer can be
observed by a section TEM (Transmission Electron Microscopy). When
very thin oxide layers are an oxide layer, a nitride layer, and an
acid nitride layer, thickness can be discriminated from contrast of
a section TEM. When discernment of thickness is difficult, it is
also possible to determine the thickness by EDX (Energy Dispersive
X-ray spectroscopy) analysis which extracted a diameter of a beam
to about 1 nm. In this case, it is also possible to calculate from
a half width of the concentration distribution, of oxygen nitrogen,
phosphorous, or fluorine while setting the measurement points at
intervals of 0.5 nm -1 nm in the film growth direction, and
plotting element distribution to a measurement positions.
[0219] When a very thin oxide layer consists of oxide or
oxinitride, it is most preferred that the high Tc material located
upper and lower side is Co or contains Co or Co. As a second
choice, nickel or its alloy are preferable, then as a third choice,
iron or its alloy are preferable. This is because Co is most hard
to oxidize and Ni is harder to oxidize than iron. By preventing
oxidization, the steep nature of an interface with a very thin
oxide layer can be held, and diffusion of oxygen can be prevented.
A structure element of a magnetic material which exists in the
upper and lower sides of a very thin oxide layer is discriminable
with the nano-EDX scan of a sectional TEM sample etc.
[0220] When a very thin oxide layer consists of an oxide layer or
an add nitride layer, as for a very thin oxide layer, it is
desirable to include material which combines with oxygen stably,
and especially at least one element among Al, Si, Mg, Ti, V, Cr,
Mn, Fe, Ta, Zr, Hf, and W is preferred.
[0221] In order to form a stable oxide layer or a stable nitride
layer, high energy oxidization or a high energy nitride process
which are mentioned later are preferred. In that case, when Ar ion
beam is used, Ar is contained in the very thin oxide layer in a
relatively higher concentration. This content Ar may add a
secondary effect to an effect of a very thin oxide layer. In order
to acquire such secondary effect, it is desirable for a very thin
oxide layer TB to contain Ar more than twice, more desirably three
times, compared with the magnetic layers of its upper and lower
sides.
[0222] A copper (Cu) layer on the pinned layer P is a non-magnetic
spacer layer S which divides the pinned layer P and the free layer
F magnetically. Instead of copper (Cu), gold (Au), silver (Ag), a
ruthenium (Ru), rhodium (Rh), palladium (Pd), etc. can also be
used. It is needed that thickness of a spacer layer S is shorter
than spin diffusion length in a pinned layer P and a free layer F
mentioned later. For example, spin diffusion length of nickel iron
(NiFe) is about 5 nm. From the viewpoint, as for the thickness of
the spacer layer S, thinner is better.
[0223] If resistance in case a conduction electron passes a spacer
layer S is high, a problem that MR rate of change falls will arise.
Also from this viewpoint, the thinner is better as for the
thickness of the spacer layer S.
[0224] On the other hand, also when the magnetization direction of
a free layer F changes with medium magnetic fields, magnetic
coupling between a pinned layer P and a free layer F must be
divided so that change may not arise in the magnetization direction
of a pinned layer P.
[0225] Thus, considering a viewpoint of dividing magnetic coupling
between the pinned layer P and the free layer F, the spacer layer S
needs to have a certain thickness.
[0226] In the case of a spacer layer S formed only with metal,
about 1.5 nm of the thickness is the minimum of the thickness.
Therefore, as thickness of a spacer layer S, 1.5 nm -5 nm is
desirable, and 2 nm -4 nm is still more desirable.
[0227] However, in order to constrict the current path in a spacer
layer S in the case of CCP-CPP (Current Confined Path Current
Perpendicular to Plane) type structure which is mentioned in the
next example, an oxide is included in a spacer layer S. In the case
of such CCP-CPP type structure, magnetic coupling between a pinned
layer P and a free layer F tends to be weak by existence of an
oxide layer which produces the CCP effect. Therefore, it becomes
possible to make the thickness of the copper (Cu) layers which
exist in the upper and lower sides of the CCP spacer thinner than
1.5 nm. For example, it becomes possible to make then thickness of
the copper (Cu) spacer layers in the upper and lower sides of an
oxide layer for CCP down to 0.1 nm.
[0228] As an oxide layer which produces the CCP effect, a tantalum
(Ta) oxide, a chromium (Cr) oxide, a titanium (Ti) oxide, a
zirconium (Zr) oxide, a hafnium (Hf) oxide, an aluminum (Al) oxide,
a silicon (Si) oxide, a magnesium (Mg) oxide, a vanadium (V) oxide,
a tungsten (W) oxide, a molybdenum (Mo) oxide, etc. can be
mentioned. Thickness of the oxide layer at this time is preferably
about 1 nm -3 nm.
[0229] Table 6 shows examples of the spacer layer S.
[0230] The invention makes it a main purpose to pull out the CPP
effect. However, in the case of the TMR (Tunneling
Magnetoresistance) effect, the conduction half metal effect of the
invention is also effective. The non-magnetic spacer layer in TMR,
such Al.sub.2O.sub.3, MgO, SiO.sub.2, HfO.sub.2, and SrTiO.sub.3,
can be used as a very thin oxide layer TB of the invention. In this
case, 1 nm -3 nm is desirable as the thickness of the oxide layer.
Since there are restrictions that resistance must not be increased
as already stated in applying to a magnetic head, the desirable
thickness may be 1 nm -2 nm.
[0231] The cobalt iron (CoFe) 1 nm/nickel iron (NiFe) 4 nm on the
spacer layer S are free layers F. It is the layer at which the
magnetization direction changes with medium magnetic fields. The
cobalt iron (CoFe) 1 nm/nickel iron (NiFe) 4 nm are the standard
free layers currently used from a generation of CIP
(Current-In-Plane) type.
[0232] In this case, the cobalt iron (CoFe) layer of 1 nm-thick at
the interface with the spacer layer S is an interface layer for
suppressing a mixing of the spacer layer S and the nickel iron
(NiFe) layer. The nickel iron (NiFe) layer is a soft magnetic
layer.
[0233] However, it may differ from a CIP type and, in a CPP type
case, a layer of 1 nm (CoFe) of cobalt iron between a spacer layer
S and a free layer F may not necessarily be needed. The spin
dependent interface scattering effect between the spacer layer S
and the free layer F in the state where current concentrated on the
spacer layer S is produced in a case of CIP type element. On the
other hand, the spin dependent interface dependence scattering
effect is produced when current passes through between interfaces
of the spacer layer S and the free layer F compulsorily in the case
of CPP type element. A mixing layer of a nickel iron (NiFe) layer
and a copper (Cu) layer may not reduce the spin dependent interface
dependence scattering effect. That is, the mixing effect would nor
be the same for CIP type and for CPP type structure.
[0234] As composition of nickel iron (NiFe),
nickel70Fe30-nickel90Fe10 is preferred, and the range of
nickel78Fe22-nickel83Fe17 is still more preferred. As film
structure which raises the spin dependent bulk scattering effect in
inside of the free layer F, a nickel iron cobalt (NiFeCo) film,
cobalt iron (CoFe)/nickel iron cobalt (NiFeCo) laminated
constitution, (NiFeCo/Cu0.1 nm).times.n laminated structure, etc.
can be mentioned.
[0235] As the composition of the nickel iron cobalt (NiFeCo) layer,
the composition around nickel66Fe16Co18 is preferable, because at
that composition, fee structure appears and magnetic distortion
tends to become zero. As for thickness of copper (Cu) when
laminating copper (Cu) on nickel iron cobalt (NiFeCo), it is
preferred to set it down to a very thin level, to about 0.1 nm -1
nm. By inserting such a very thin copper (Cu) layer, the spin
dependent bulk scattering effect in the inside of the free layer F
increases, and MR rate of change increases. Since magnetic coupling
of a magnetic layer of the upper and lower sides through the copper
layer will go out if copper (Cu) thickness becomes thicker than 1
nm too much, and it stops functioning as the united free layer F,
it is not desirable.
[0236] Since a cycle of inserting copper (Cu) layers to the free
layer F also brings a difference to MR rate of change, it is
important. As a thickness interval to insert the copper (Cu) layers
repeatedly, 0.5 nm -3 nm is preferred, and 0.7 nm -2 nm is more
preferred.
[0237] Not only a case of nickel iron cobalt (NiFeCo) but also in
the case of nickel iron (NiFe), insertion, of such a very thin
copper (Cu) layer brings about MR rate of change. Therefore,
(NiFe/Cu).times.n laminated structure may be adopted. A single
layer of CoFe can also be used as a free layer. A laminated
structure of (CoFe/Cu).times.n can also be used. As the inserting
layer for such a laminated structure, a layer made of copper (Cu),
zirconium (Zr), hafnium (Hf), niobium (Nb), or material like
gallium (Ga) is usable. The thickness of these inserting layers may
preferably in a range 0.1 nm-1 nm. By inserting such a layer into
the free layer, spin-dependent bulk scattering effect in the free
layer may be enhanced, and thus, MR may be improved.
[0238] In this example, a magnetic layer is not mixed as an
addition element, but very thin layers are inserted at intervals of
a certain fixed thickness. In such a case, it is desirable to
insert element material which does not form a solid solution with
the element which constitutes the magnetic layer. For example, when
a zirconium (Zr), a hafnium (Hf), etc. are used, MR rate of change
improves and it is especially desirable.
[0239] Such existence of a very thin metal layer can be observed by
a section TEM (Transmission Electron Microscopy) from a film
section etc. even after the heat treatment for magnetization
pinning of an antiferromagnetic layer in a magnetic field. When it
contained as an addition element simply in a magnetic layer, big
concentration distribution is not seen in the direction of a film
section. On the other hand, when it inserts as an independent layer
like this example, it can observe by a section TEM. By using a
nano-EDX (energy dispersive x-ray spectroscopy) of about 1 nm of
diameters of beam spot (it is more desirable as smaller than this
diameter of spot) is observable as concentration distribution of a
structure element by measuring at intervals of 1 nm or less in the
direction of thickness.
[0240] However, as mentioned above, the inserted thickness may be
about 0.1 nm. When EDX analysis of such a very thin layer is
carried out with about 1 nm of diameters of beam spot, as a result
of EDX analysis, it will be detected as concentration of number
atom % also in an area in which a very thin layer exists. However,
it is possible by scanning the same measurement in the direction of
thickness to identify in an area where a very thin, layer element
layer exists, and an area which is not carried out.
[0241] Table 7 shows the examples of other free layer F.
[0242] In this example, a copper (Cu) layer laminated on a free
layer F functions also as a prevention layer of interface mixing
with tantalum on it (Ta). Instead of copper (Cu), gold (Au), silver
(Ag), a ruthenium (Ru), rhodium (Rh), palladium (Pd), etc. may be
used. This layer can also be lost, when interface mixing with a cap
layer is prevented. As for the thickness of this layer, it is
preferred that it is 0 nm-about 3 nm.
[0243] A copper (Cu) layer on a free layer F and a tantalum (Ta)
layer laminated on it are called a "cap layer" here. This is for
protecting so that a lamination film may not be etched, also when
the micro fabrication process after spin valve film formation is
performed. Instead of a tantalum (Ta) layer, titanium (Ti),
zirconium (Zr), ruthenium (Ru), niobium (Nb), tungsten (W), hafnium
(Hf), rhenium (Re), iridium (Ir), gold (Au), silver (Ag), etc. can
be used as a protection layer.
[0244] Table 8 shows the examples of the cap layer.
[0245] On the other hand, since controlling the crystal orientation
of a spin valve film also affects MR rate of change as mentioned
above, it is important. By controlling crystal orientation, crystal
defects within a spin dependence scattering unit of pinned layer
P/spacer layer S/free layer F may be decreased. As the result, spin
information on an up spin and a down spin is not lost, and spin
diffusion length in a laminated structure can be lengthened enough.
That is, even if total thickness of pinned layer P/spacer layer S
/free layer F becomes thick, the spin dependence bulk scattering
effect can fully be obtained, and MR rate of change improves.
[0246] The coherency of the laminated structure also improves by
controlling crystal orientation. Therefore, the spin dependent
interface scattering effect improves and MR rate of change
improves.
[0247] Good crystal band structure is formed by controlling crystal
orientation. Therefore, a band structural change by insertion of
very thin metal layers, such as a copper (Cu) layer of a very thin
and a zirconium (Zr) layer of a very thin, which was mentioned
above becomes easy to appear notably. As the result, improvement in
MR rate of change resulting from band structure becomes more
remarkable. For example, when band structure changes, a difference
of the Fermi speed of an up spin and a down spin becomes large.
This phenomenon becomes more remarkable in a spin valve film with
good crystal orientation.
[0248] The invention is an aiming at band structure modulation of a
crystal. Therefore, when crystal orientation changes, naturally an
effect of a very thin oxide layer will change. When a pinned layer
P or a free layer F has fee structure, it is desirable to have fcc
(111) orientation. When a pinned layer P or a free layer F has bcc
structure, it is desirable to have bcc (110) orientation. When the
pinned layer P or the free layer F has hcp structure, it is
desirable to have for hcp (001) orientation or hcp (110)
orientation.
[0249] As for the orientation variation angle, it is preferred that
it is less than 5.0 degrees, and it is still preferred that it is
less than 3.5 degrees and it is still more preferred that it is
less than 3.0 degrees, and that it is most preferred that it is
less than 4.0 more degrees. A film having an excellent crystal
orientation can obtain high MR rate of change. That is, high output
voltage can be obtained.
[0250] This reason is explained below. The very thin oxide layer in
the invention aims at modulating the band structure of a magnetic
layer. Band structure can be defined about what naturally has a
crystal structure. That is, more perfect crystal structure is
acquired, the effect of the band modulation of a the invention
shows up more notably, and the rise effect of MR rate of change
becomes larger. The quality of a crystal corresponds to a
distribution angle of the crystal orientation. Therefore, the band
modulation effect by the invention becomes large and MR rate
becomes large, as the distribution angle becomes small.
[0251] Concretely, when the distribution angle 6 degrees, the
increasing rate of MR rate of change by having inserted the very
thin oxide layer by the invention was as small as about 1.1 times.
On the other hand, when the distribution angle was 5 degrees, the
increasing rate of MR was twice. Moreover, when the distribution
angle was 4 degrees, the increasing rate of MR was three times.
When the distribution angle was 3.5 degrees, the increasing rate of
MR was 4 times. When the distribution angle was 3 degrees, the
increasing rate of MR was 5 times. These data were obtained with
samples where only one very thin oxide layer was inserted.
Therefore, by inserting two or more very thin oxide layers, further
improvement can be attained.
[0252] In measurement by X-rays, crystal orientation can be
measured as half width of a rocking curve in a peak position
obtained by .theta.-2.theta. measurement. In a magnetic head, it is
detectable as a distribution angle of a spot in a nano-diffraction
pattern taken from section structure. As for the crystal
orientation of the polycrystalline films, the definition of the
terms and its measurement procedures, those described in U.S. Pat.
No. 6,395,388 can be referred to. The entire contents of this
reference is incorporated herein by reference.
[0253] Although it is dependent also on material of an
antiferromagnetic film, generally the lattice spacing of the
antiferromagnetic film differs from lattice spacing of pinned layer
P /spacer layer S/free layer F. Therefore, it is possible to
calculate separately a variation angle for orientation in each
layer.
[0254] For example, platinum manganese (PtMn), and pinned layer
P/spacer layer S/free layer F become the structure that lattice
spacing differ, in many cases. Since platinum manganese (PtMn) is
formed comparatively thickly, it is the material suitable for
measuring the crystal orientation variation. As for pinned layer P
/spacer layer S/free layer F, crystal structures of a pinned layer
P and a free layer F may differ like bcc structure and fee
structure. Therefore, the pinned layer P and the free layer F have
a distribution angle s for respectively different crystal
orientations.
[0255] Next, an example about a formation method of a very thin
oxide layer TB in the embodiment will be explained.
[0256] FIG. 24 is a conceptual diagram showing an example of a
formation apparatus which forms a magnetoresistance effect element
containing a very thin oxide layer TB in the embodiment. That is,
in the case of a apparatus of this figure, it has structure where a
load lock chamber LC which introduces a substrate, film formation
chambers MC1, MC2, and TBC, a surface treatment chamber PC, etc.
are connected via a vacuum valve V, via a transfer chamber TC.
[0257] In metal film formation chambers MC1 and MC2, film formation
of a metal film used as a basic unit of a spin valve film is formed
with methods for film deposition, such as a sputtering.
Specifically, sputtering film formation of various kinds of methods
of DC magnetron film formation, RF magnetron sputtering, and others
and IBD (Ion Beam Deposition) may be used. Vapor deposition film
formation, MBE (Molecular Beam Epitaxy), etc. may also be used. A
very thin oxide layer TB in the embodiment, such as an oxide layer
and a nitride layer, may be formed by these film formation
chambers.
[0258] It is also the desirable manufacture method of a very thin
oxide layer, to perform formation of an oxide layer used as a very
thin oxide layer TB of the embodiment or a nitride layer in a
surface treatment chamber PC on the other hand. Specifically,
natural oxidation, the natural nitriding method, UV (ultraviolet
rays) light irradiation in the radical oxidizing (nitride) method
and oxygen atmosphere, the ozone oxidizing method, the ion beam
oxidizing method, etc. can be used.
[0259] The oxidization technique with the energy assistant effect
is more desirable than a natural oxidation method. For example,
since the ion beam oxidizing method etc. has the energy assistant
effect by an ion beam, it is effective. Then, oxygen gas may be
irradiated as an ion beam and an ion beam of rare gas, such as
argon (Ar), xenon (Xe), and krypton (Kr), may be irradiated in
oxygen atmosphere.
Since thickness of an oxide layer or a nitride layer will become
thick if energy of a beam is too high at this time, the degree of
beam incidence angle also has low angle incidence more preferred
than perpendicular incidence with energy of a grade which is not
too high.
[0260] For example, in the case of 90-degree incidence, 50V-150V
have the desirable degree of incidence angle as accelerating
voltage of an ion beam to the main side of a substrate, and when
the degree of incidence angle is the low angle incidence which is
10-30 degrees, about 50-300V is desirable as accelerating voltage
of an ion beam.
[0261] However, in oxidization and a nitride using the conventional
ion beam, energy spreads in the direction as the degree of beam
incidence angle where energy of a beam is; the same.
Therefore, even if the accelerating voltage of a beam is lowered or
the degree of incidence angle is made into low angle incidence, it
arises that thickness of an oxide film becomes thick depending on
material of the surface which oxidizes. As a method of controlling
this further, a method of using GC-IB (Gas Cluster Ion-Beam) which
is the ion beam of a cluster state instead of an ion beam of the
conventional monomer can be mentioned.
[0262] In the case of this method, when it is accelerated in the
state of a cluster and an ion beam collides with the sample
surface, a cluster bursts with quantity of motion in the direction
of the film surface. Thus, a high-concentration gas molecule has
the energy to the direction of a film plane (getting it blocked and
there being no damage to the direction of thickness), and collides.
If an oxygen cluster is used as a gas molecule, it is compatible in
oxide formation by high energy oxidization and formation in a very
thin level. By adjusting the number of gas clusters, oxygen
concentration per unit surface area can be adjusted. Therefore, the
valence number can be also controlled.
Second Example
[0263] Next, the example of the CPP type magnetoresistance effect
element which can be used as a magnetic head is given and explained
as the second example of the invention.
[0264] FIGS. 25 and 26 are conceptual diagrams which express
typically the principal part structure of the magnetoresistance
effect element concerning the embodiment of the invention. That is,
these figures express the state where the magnetoresistance effect
element is included in the magnetic head. FIG. 25 is a sectional
view of the magnetoresistance effect element cut in parallel to the
medium facing surface P which is opposite to a magnetic recording
medium (not shown). FIG. 26 is a sectional view of the magnetic
resistance effect element cut in the perpendicular direction to the
medium opposite side P.
[0265] The magnetoresistance effect element illustrated in FIGS. 25
and 26 has a hard abutted structure. The lower electrode 2 and the
upper electrode 6 are provided in the upper and lower sides of the
magnetoresistance effect film 4, respectively. Moreover, as
expressed in FIG. 25, the bias magnetic field applying film 10 and
the insulating film 12 are laminated and provided in the both sides
of the magnetoresistance effect film 4. Furthermore, as illustrated
in FIG. 26, the protection layer 8 is provided in the medium facing
surface of the magnetoresistance effect film 4.
[0266] The magnetoresistance effect film 4 has the structure
according to the embodiment of the invention mentioned above
referring to FIGS. 1 and 24. That is, the very thin oxide layer is
suitably inserted in the magnetoresistance effect film, and a large
resistance change can be obtained by CPP type current supply.
[0267] The sense current to the magnetoresistance effect film 4 is
passed in a perpendicular direction to the film plane, as indicated
by the arrow A, with the electrodes 2 and 6 arranged at the upper
and lower sides. Moreover, a bias magnetic field is applied to the
magnetoresistance effect film 4 with a pair of bias magnetic field
applying films 10 and 10 provided in right and left.
[0268] By this bias magnetic field, magnetic anisotropy of the free
layer of the magnetoresistance effect film 4 can be controlled and
formed into a single magnetic domain. As a result, magnetic domain
structure can be stabilized, and the Barkhausen noise due to the
movement of magnetic wall can be suppressed.
[0269] According to the invention, MR rate of change improves by
providing the very thin oxide layer suitably in the
magnetoresistance effect film 4. As a result, it becomes possible
to improve the to sensitivity of a magnetoresistance effect element
notably. And for example, when it is applied to a magnetic head,
magnetic reproduction of high sensitivity is attained.
Third Example
[0270] Next, a magnetic reproducing apparatus having inboard the
magnetoresistance effect element of the embodiment will be
explained as the third example of the invention.
[0271] That is, the magnetoresistance effect, element or the
magnetic head explained with reference to FIGS. 1 through 26 can be
incorporated in a recording/reproducing magnetic head assembly and
mounted in a magnetic reproducing apparatus.
[0272] FIG. 27 is a perspective view that shows outline
configuration of this kind of magnetic reproducing apparatus. The
magnetic reproducing apparatus 150 shown here is of a type using a
rotary actuator. A magnetic reproducing medium disk 200 is mounted
on a spindle 152 and rotated in the arrow A direction by a motor,
not shown, which is responsive to a control (signal from a
controller of a driving mechanism, not shown. The magnetic
reproducing apparatus 150 shown here may have a plurality of medium
disks 200 inboard.
[0273] The medium disk 200 may be of a "lateral recording type" in
which directions of the recording bits are substantially in
parallel to the disk surface or may be of a "perpendicular
recording type" in which directions of the recording bits are
substantially perpendicular to the disk surface.
[0274] A head slider 153 for carrying out recording and
reproduction of information to be stored in the medium disk 200 is
attached to the tip of a film-shaped suspension 154. The head
slider 153 supports a magnetoresistance effect element or magnetic
head, for example, according to one of the foregoing embodiments of
the invention, near the distal end thereof.
[0275] Once the medium disk 200 rotates, the medium-facing surface
(ABS) of the head slider 153 is held floating by a predetermined
distance above the surface of the medium disk 200. Also acceptable
is a so-called "contact-traveling type" in which the slider
contacts the medium disk 200.
[0276] The suspension 154 is connected to one end of an actuator
arm 155 having a bobbin portion for holding a drive coil, not
shown, and others. At the opposite end of the actuator arm 155, a
voice coil motor 156, a kind of linear motor, is provided. The
voice coil motor 156 comprises a drive coil, not shown, wound on
the bobbin portion of the actuator arm 155, and a magnetic circuit
made up of a permanent magnet and an opposed yoke that are opposed
to sandwich the drive coil.
[0277] The actuator arm 155 is supported by ball bearings, not
shown, which are located at upper and lower two positions of the
spindle 157 and driven by the voice coil motor 156 for rotating,
sliding movements.
[0278] FIG. 28 is a perspective view of a magnetic head assembly at
the distal end from an actuator arm 155 involved, which is viewed
from the disk. The magnetic head assembly 160 includes the actuator
arm 155 having the bobbin portion supporting the drive coil, for
example, and the suspension 154 is connected to one end of the
actuator arm 155.
[0279] At the distal end of the suspension 154, a head slider 153
carrying the magnetoresistance effect element as explained with
reference to FIGS. 1 through 24 is provided. The suspension 154 has
a lead 164 for writing and reading signals, and the lead line 164
is connected to electrodes of the magnetic head incorporated in the
head slider 153. Numeral 165 in FIG. 28 denotes an electrode pad of
the magnetic head assembly 160.
[0280] According to this example, one of the magnetoresistance
effect elements already explained in conjunction with the
aforementioned embodiments is used as the magnetoresistance effect
element, information magnetically recorded on the medium disk 200
under a higher recording density than before can be read
reliably.
Fourth Example
[0281] Next, a magnetic memory having the magnetoresistance effect
element of the embodiment will be explained as the fourth example
of the invention. That is, a magnetic memory, such as a magnetic
random access memory (MRAM), where memory cells are arranged in the
shape of a matrix can be realized by using the magnetoresistance
effect element of the embodiment.
[0282] FIG. 29 is a conceptual diagram which exemplifies the matrix
structure of the magnetic memory of the embodiment. That is, this
figure shows the circuit structure of the embodiment in the case of
having arranged the memory cells each of which includes a
magnetoresistance effect element mentioned above with reference to
FIGS. 1 through 24, in the shape of a matrix array.
[0283] In order to choose one bit in an array, it has the sequence
decoder 350 and the line decoder 351, By selecting the bit line 334
and the word line 332, specific switching transistor 330 is turned
on and a specific cell is chosen uniquely. And the bit information
recorded on the magnetic-recording layer which constitutes the
magnetoresistance effect element 321 can be read by detecting with
a sense amplifier 352.
[0284] When writing in bit information, writing current is passed
in the specific write-in word line 323 and the specific bit line
322, respectively, and the current magnetic field is applied to the
recording layer of a specific cell.
[0285] FIG. 30 is a conceptual diagram showing another example of
the matrix structure of the magnetic memory of the embodiment. That
is, in the case of this example, the bit lines 322 and word lines
334 which were wired in the shape of a matrix are chosen by
decoders 360 and 361, respectively, and the specific memory cell in
an array is chosen uniquely.
[0286] Each memory cell has the structure where Diode D is
connected with the magnetoresistance effect element 321 in series.
Here, Diode D has the role to prevent that sense current detours in
memory cells other than magnetoresistance effect element 321
selected.
[0287] In writing, write-in current is passed in a specific bit
line 322 and a word line 323, thereby applying the current magnetic
field to the recording layer of a specific cell.
[0288] FIG. 31 is a conceptual diagram showing a principal part of
the cross sectional structure of a magnetic memory according to an
embodiment of the invention.
[0289] And FIG. 32 shows the A-A' line sectional view.
[0290] That is, the structure shown in these figures corresponds to
the memory cell of the 1-bit portion of the magnetic memory which
operates as a random access memory.
[0291] This memory cell consists of a storage cell portion 311 and
a transistor portion 312 for address selection. The storage cell
portion 311 has the magnetoresistance effect element 321 and a pair
of wiring 322 and 324 connected to the element 321. The
magnetoresistance effect element 321 has a structure mentioned with
reference to FIGS. 1 through 24, and shows a large
magnetoresistance effect.
[0292] What is necessary is to pass sense current for the
magnetoresistance effect element 321 in the case of bit information
read-out, and just to detect the resistance change. In addition,
the magnetization free layer of the magnetoresistance effect
element can be used as the magnetic recording layer.
[0293] If the element 4 has a ferromagnetic double tunnel junction
structure such as magnetic layer/non-magnetic tunnel layer
/magnetic layer/non-magnetic tunnel layer/magnetic layer etc., it
is advantageous at a point that the high magnetoresistance effect
is acquired by a large resistance change by the tunnel
magnetoresistance (TMR) effect.
[0294] In such structures, one of magnetic layers shall act, as a
magnetization pinned layer, and one of other magnetic layers shall
act as a magnetic record layer.
[0295] A selecting transistor 330 connected through a via 326 and
buried wiring 328 is formed in a transistor portion 312 for
selection. This transistor 330 carries out switching operation
according to the voltage applied to a gate 332, and controls
switching of the current path between the magnetoresistance effect
element 321 and wiring 334.
[0296] Moreover, under the magnetoresistance effect element, the
write-in wiring 323 is formed in the direction which intersects the
wiring 322. These write-in wirings 322 and 323 can be formed with
the alloy containing aluminum (aluminum), copper (Cu), tungsten
(W), tantalum (Ta), or one of these.
[0297] In a memory cell of such structure, when writing bit
information in the magnetoresistance effect element 321, a write-in
pulse current is passed to the wirings 322 and 323. Then, a
synthetic magnetic field induced by these current is applied to a
record layer, and magnetization of a record layer of the
magnetoresistance effect element can be reversed suitably.
[0298] On the other hand, when reading bit information, sense
current is passed through wiring 322, the magnetoresistance element
321 containing a magnetic-recording layer, and the lower electrode
324, and a change of the resistance of the magnetoresistance effect
element 321 or resistance itself is measured.
[0299] By using the magnetoresistance effect element mentioned with
reference to FIGS. 1 through 24, a large magnetoresistance effect
is obtained. Therefore, a stable read-out can be performed even if
the cell size is reduced to realize a large capacity storage.
[0300] Heretofore, embodiments of the invention have been explained
in detail with reference to some specific examples. The invention,
however, is not limited to these specific examples.
[0301] For example, material, shape and thickness of the
ferromagnetic layer, anti-ferromagnetic layer, insulating film and
very thin oxide layer of the magnetoresistance effect element
according to the invention may be appropriately selected by those
skilled in the art within the known techniques to carry out the
invention as taught in the specification and obtain equivalent
effects.
[0302] Further, in a case where the magnetoresistance effect
element of the invention is applied to a magnetic head, by
providing magnetic shields on upper and lower side of the element,
the reproducing resolution can be regulated.
[0303] It will be also appreciated that the invention is applicable
not only to optically-assisted magnetic heads or magnetic recording
apparatuses of the lengthwise recording type but also to those of
the perpendicular magnetic recording type and ensures substantially
the same effects.
[0304] Further, the magnetic reproducing apparatus according to the
present invention may be of a fixed type in which specific magnetic
recording medium is permanently installed, while it may be of a
removable type in which the magnetic recording medium can be
replaced easily.
[0305] Further, also concerning the magnetic memory according to
the invention, those skilled in the art will be able to carry out
the invention by appropriately selecting a material or a structure
within the known techniques.
[0306] While the present invention has been disclosed in terms of
the embodiment in order to facilitate better understanding thereof,
it should be appreciated that the invention can be embodied in
various ways without departing from the principle of the invention.
Therefore, the invention should be understood to include all
possible embodiments and modification to the shown embodiments
which can be embodied without departing from the principle of the
invention as set forth in the appended claims.
TABLE-US-00001 TABLE 1 EFFECT OF THE LAYER TB 1. SHIFT OF DOS 2.
DIFFERENCE IN FERMI SPEEDS v.sub.f.sup..uparw. and
.gradient..sub.f.sup..dwnarw. .dwnarw. by combining these two
effects spin polarization changes and half metallic property
generated .dwnarw. increase in MR ratio no increase in CPP
resistance
TABLE-US-00002 TABLE 2 Ta 1~6 nm/NiFe 2~5 nm (Ta can be omitted.
Zr, Cr, W, Hf, V or Ti can be used instead of Ta.) Ta 1~6 nm/NiFeCr
2~7 nm (Cr concentration: 5~45atomic %) (Ta can be omitted. Zr, Cr,
W, Hf, V or Ti can be used instead of Ta.) Ta 1~6 nm/NiFeCr 2~7
nm/NiFe 0.5~2 nm (Cr concentration: 5-45atomic %) (Ta can be
omitted. Zr, Cr, W, Hf, V or Ti can be used instead of Ta.) Ta 1~6
nm/Ru, Cu, Ir. etc.: 2~5 nm (Ta can be omitted. Zr, Cr, W, Hf, V or
Ti can be used instead of Ta.) Ta 1~6 nm/NiCr 2~5 nm (Ta can be
omitted. Zr, Cr, W, Hf, V or Ti can be used instead of Ta.) Ta 1~6
nm/NiFe 2~5 nm/current constriction layer 0.5~3 nm/Cu 0~2 nm (Ta
can be omitted. Zr, Cr, W, Hf, V or Ti can be used instead of Ta.)
(current constriction layer: oxide of Al, Cr, Mg Hf, etc., Au, Ag,
Ru, Rh or Re can be used instead of Cu.) (In order to improve the
quality of the free layer, Cu layer may preferably be thicker than
0.1 nm.) Ta 1~8 nm/NiFeCr 2~5 nm/current constriction layer 0.5~2
nm/Cu 0~2 nm (Ta can be omitted. Zr, Cr, W, Hf, V or Ti can be used
instead of Ta.) (current constriction layer. oxide of Al, Cr, Mg,
Hf, etc. Au, Ag, Ru, Rh or Re can be used instead of Cu.) (In order
to improve the quality of the free layer, Cu layer may preferably
be thicker than 0.1 nm.)
TABLE-US-00003 TABLE 3 antiferromagnetic layer (PtMn, IrMn, PdPtMn,
RuRhMn, etc.) 5~30 nm antiferromagnetic layer (PtMn, IrMn, PdPtMn,
RuRhMn, etc.) 5~30 nm/ ferromagnetic layer (CoFe, FeCo, NiFe, etc.)
2~7 nm/Ru 0.9 nm/ hard magnetic layer (CoPt, CoCrPt, FePt, Co etc.)
5~30 nm
TABLE-US-00004 TABLE 4 NiFe 2~12 nm (Ni:Fe = 0:100~100.0) CoFe 2~12
nm (Co:Fe = 0:100~100:0) FeCo 2~12 nm (Fe:Co = 0:100~100:0) NiFeX
2~12 nm (Ni:Fe = 0:100~100:0) (X = Al, Si, Ti, V, Cr, Mn, Co, Cu,
Zn, Ga, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, Au,
etc.) CoFeX 2~12 nm (Co:Fe = 0:100~100:0) (X = Al, Si, Ti, V, Cr,
Mn, Co, Cu, Zn, Ga, Zr Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os,
Ir, Pt, Au, etc.) FeCoX 2~12 nm (Fe:Co = 0:100~100:0) (X = Al, Si,
Ti, V, Cr, Mn, Co, Cu, Zn, Ga, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta,
W, Re, Os, Ie, Pt, Au, etc.) NiFeX 2~10 nm/CoFe 0.5~3 nm (Ni:Fe =
75:25~87:13, Co:Fe = 85:15~95:5) Ni.sub.xFe.sub.yCo.sub.100-(x+y)
3~12 nm (x:y = 65:35~90:10, x + y = 99~70
Ni.sub.xFe.sub.yCo.sub.100-(x+y) 3~12 nm/CoFe 0.5~3 nm (x:y =
65:35~90:10, Co:Fe = 85:15~95:5) Co.sub.xFe.sub.yNi.sub.100-(x+y)
3~12 nm (x:y = 70:30~93:7, x + y = 99~80)
Co.sub.xFe.sub.yB.sub.100-(x+y) 3~12 nm (x:y = 80:20~93:7, x + y =
99~90) NiFe 2~10 nm/CoFeNi 0.5~3 nm (Ni:Fe = 75:25~87:13) NiFe 2~10
nm/FeCo 0.5~3 nm (Ni:Fe = 75:25~87:13) FeCo 2~7 nm (Fe:Co =
80:20~30:70, preferably Fe:Co = 60.40~40.60, FeCo may preferably
have a bcc structure.) (FeCo 0.8~2 nm/Cu 0.1~1 nm) .times. N (N =
2~8, total thickness: 2~7 nm, Fe:Co = 80:20~30:70, preferably FeCo
= 60:40~40:60. FeCo may preferably have a bcc structure.)
Fe.sub.xCo.sub.yNi.sub.100-(x+y) 2~7 nm (x:y = 40.80~70:30, x + y =
50~99, FeCoNi may preferably have a fcc structure.) (FeCoNi 0.8~2
nm/Cu 0.1~1 nm) .times. N (N = 2~8, total thickness: 2~7 nm, x:y =
40:60~70:30, x + y = 50~99, FeCoNi may preferably have a fcc
structure.) (Zr, Hf, Pd or Rh can be used instead of Cu.)
Fe.sub.xCo.sub.yNi.sub.100-(x+y) 2~7 nm/CoFe 0.5 nm~3 nm (x:y = 40
60~70:30, x + y = 50~99, FeCoNi may preferably have a fcc
structure. FeCo can be used instead of CoFe.) (FeCoNi 0.8~2 nm/Cu
0.1~1 nm) .times. N/CoFe 0.5~3 nm (N = 2~8, total thickness: 2~7
nm, x:y = 40:60~70:30, x + y = 50~99, FeCoNi may preferably have a
fcc structure. FeCo can be used instead of CoFe.) (Zr, Hf, Pd or Rh
can be used instead of Cu.)
TABLE-US-00005 TABLE 5 oxide, nitride oxinitride, phosphide, or
flouride including at least one of Al, Ti, V, Cr, Mn, Fe, Co, Ni,
Cu: 0.2 nm-3 nm (preferably in a rage of 0.2 nm-2 nm) oxide,
nitride oxinitride, phosphide, or flouride including at least one
of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu: 0.2 nm-3 nm (preferably in a
range of 0.2 nm-2 nm) (film is not uniform. oxides, nitrides, etc.
scatters discontinously in the film.) oxide, nitride, oxinitride,
phosphide, or fluoride including at least one of Zr, Nb, Mo, To,
Ru, Rh, Pd, Ag, Hf, Ta, W, Re,, Os: 0.2 nm-3 nm (preferably in 0.2
nm-2 nm) oxide, nitride, oxinitride, phosphide, or fluoride
including at least one of Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta,
W, Re, Os, Ir, Pt, Au: 0.2 nm-3 nm) (film is not uniform. oxides,
nitrides, et. scatters discontinously in the film.)
TABLE-US-00006 TABLE 6 Cu 1.5~7 nm Au, Ag, Pd, Ru, Rh, Re, Cr,
etc.: 1.5~7 nm Alloys including at least one of Cu, Au, Ag, Pd, Ru,
Rh, Re, Cr: 1.5~7 nm Cu 0.1 nm~2 nm/current constriction layer
0.5~3 nm/Cu 0.1 nm~2 nm (current constriction layer: aluminum
oxide, chromium oxide, etc. Au, Ag, Ru, Rh or Re can be used
instead of Cu) (In order to improve the quality of the free layer
and the pinned layer, Cu may preferably be thicker than 0.1
nm.)
TABLE-US-00007 TABLE 7 NiFe 3~12 nm (Ni:Fe = 75:25~87:13) CoFe
0.5~3 nm/NiFe 2~10 nm (Co:Fe = 85:15~95:5, Ni:Fe = 75:25~87:13)
Ni.sub.xFe.sub.yCo.sub.100-(x+y) 3~12 nm (x:y = 85:35~90:10, x + y
~ 99~70) CoFe 0.5~3 nm/Ni.sub.xFe.sub.yCo.sub.100-(x+y)3~12 nm
(Co:Fe = 85.15~95:5, x:y = 65:35~90:10)
Co.sub.xFe.sub.yNi.sub.100-(x+y) 3~12 nm (x:y = 70:30~93:7, x + y =
99~80) Co.sub.xFe.sub.yB.sub.100-(x+y) 3~12 nm (x:y = 80:20~93:7, x
+ y = 99~90) CoFeNi 0.5~3 nm/NiFe 2~10 nm (Ni:Fe = 75:25~87:13)
FeCo 0.5~1 nm/NiFe 2~10 nm (Ni:Fe = 75:25~87:13) (NiFe 0.8 nm~3
nm/Cu 0.1 nm~2 nm) .times. N (N = 2~6, total thickness: 3~12 nm)
Ni:Fe = 75:25~87:13, Zr, Hf, Rh, Ru can be used instead of Cu)
(CoFe 0.5~3 nm/NiFe 0.8 nm~3 nm/Cu 0.1 nm~2 nm) .times. N (N = 2~8,
total thickness: 3~12 nm) (Ni:Fe = 75:25~87:13, Zr, Hf, Rh, Ru can
be used instead of Cu.)
TABLE-US-00008 TABLE 8 Ta 1~10 nm (Ti, Cr, W, Hf, Zr, V, Cu, Au, Ag
can be used instead of Ta.) Cu 0.5~5 nm/Te 1~10 nm (Au, Ag, Ru, Rh,
Re, Pt, Ir, Os can be used instead of Cu.) (Ti, Cr, W, Hf, Zr, V
can be used instead of Ta.) Alloys including at least one of Cu,
Au, Ag, Pd, Ru, Rh, Re and Cr: 1.5~7 nm Cu 0 nm~2 nm/current
constriction layer 0.5~3 nm/Cu 0 nm~2 nm (current constriction
layer; oxide of Al, Cr, Mg, Hf, etc. Au, Ag, Ru, Rh, Re can be used
instead of Cu.) (In order to improve the quality of the free layer
and pinned layer, Cu may preferably thicker than 0.1 nm.)
* * * * *